Genera sentence example
The pasto duro is largely composed of the genera Stipa and Melica.
The same deposits have also yielded remains of extinct types of kangaroo, some of gigantic size, constituting the genera Sthenurus, Procoptodon and Palorchestes.
Filhol, the fossils themselves represent two genera, Peratherium, containing the greater part of the species, about twenty in number, and Amphiperatherium, with three species only.
Of doubtful position, but commonly referred to the Trachylinae, are the two genera of fresh-water medusae, Limnocodium and Limnocnida.
In some Indian and Malay Engystomatids of the genera Callula and Microhyla, the tadpoles are remarkably transparent, and differ markedly in the structure of the buccal apparatus.Advertisement
Cells of this type are often called trumpet-hyphae (though they have no connection with the hyphae of Fungi), and in some genera of Laminariaceae those at the periphery of the medulla simulate the sieve-tubes of the higher plants in a striking degree, even (like these latter) developing the peculiar substance callose on or in the perforated cross-walls or sieve-plates.
In a good many cases, sometimes in isolated genera or species, sometimes characteristic of whole families, so-called anomalous cambial layers are formed in the stem, either as an extension of, or in addition to, the original cambial cylinder.
The former is concerned with the division of the earths surface into major districts characterized by particular plants or taxonomic groups of plants, with the subdivision of these floristic districts, and with the geographical distribution (both past and present) of the various taxonomic units, such as species, genera, and families.
Casimir de Candolle has made an independent investigation, based on Hooker and Benthams Genera plantarum.
Though now on the way to extinction, Cycadeae are still widely represented in the southern hemisphere by genera which, however, have no counterpart in the Mesozoic era.Advertisement
Amongst Conifers the archaic genera, Ginkgo and Araucarus still persist.
In the mountains of Peru we find such characteristic northern genera as Draba, Alchemilla, Saxifraga, Valeriana, Gentiana and Bartsia.
If we turn to herbaceous plants, Hemsley has pointed out that of the thirteen genera of Ranunculaceae in California, eleven are British.
Assuming that in its circumpolar origin the North Temperate flora was fairly homogeneous, it would meet in its centrifugal extension with a wide range of local conditions; these would favor the preservation of numerous species in some genera, their greater or less elimination in others.
On the other hand, it is rich in Cornpositae, especially Solidago and A ster, Polemoniaceae, Asciepiadaceae, Hydrophyllaceae and Cyperaceae, and it has the endemic Sarracenia, type of a family structurally allied to poppies, of which of the remaining genera Darlingtonia is Californian, and Heliamphora Venezuelan.Advertisement
Its arboreal vegetation is richer both in genera and species than that corresponding to it in the Old World.
Of four genera which Hooker singles out as the largest in Sikkim, in China Corydalis has 76 species, Saxifraga 58, Pedicularis 129, and Primula 77.
Amongst palms Washinglonia, Brahea and Erythea (all Corypheac) replace the eastern genera.
C. de Candolle finds that with one exception the species belong to genera represented in one or other of the Indian peninsulas.
As in the IndoMalayan sub-region, epiphytic orchids are probably most numerous in point of species, but the genera and even sub-tribes are far more restricted in their range than in the Old World; 4 sub-tribes with 74 genera of Vandeae are confined to South America, though varying in range of climate and altitude.Advertisement
Nearly related to myrtles are Melastomaceae which, poorly represented in the Old World, have attained here so prodigious a development in genera and species, that Ball looks upon it as the seat of origin of the family.
Aroids, of which the tribes are not restricted in their distribution, have two large endemic genera, Philodendron and Anthurium.
Instead of large continuous areas, in which local characteristics sometimes blend, it occupies widely dissevered territories in which specialization, intensified by long se1/2aration, hai mostly effaced the possibility of comparing species hnd even genera and compels us to seek for points of contact in groups of a higher order.
While so many conspicuous Australian elements are wanting in New Zealand, one-eighth of its flora belongs to South American genera.
By the same path it kis received a remarkable contribution from the North Temperate region; such familiar genera as Ranunculus, Epilobfum and Veronica form more than 9% of the flowering plants.Advertisement
Taking, however, the Andean flora as typical, it contains a very marked endemic element; Ball finds that half the genera and four-fifths of the species are limited to it; on the other hand, that half the species of Gamopetalae belong to cosmopolitan genera such as Valeriana, Gentiana, Bartsia and Gnaphalium.
On the other hand, it is the headquarters of Mutisiaceae, represented in South Africa by such genera as Oldenburgia and Gerbera and by Triehocline in Australia.
Prosotis extends to the Argentine; other characteristic genera are Oenothera, Godetia Collomia, Heliotropium and Eritrichium.
On the whole, it consists of local species of some widely distributed northern genera, such as Carex, Poa, Ranunculus, &c., with alpine types of strictly south temperate genera, characteristic of the separate localities.
Forbes had investigated such important genera as Philepitta and Xenicus, P.L.Advertisement
But it also follows that, if every extinct and recent bird were known, neither species, nor genera, nor families, nor orders could be defined.
Baptornis, another of Marsh's genera, seems to be allied to Enaliornis, Palaeotringa and Talmatornis, were by him referred to Limicoline and Passerine birds.
The upper Eocene has yielded many birds, most of which are at least close forerunners of recent genera, the differentiation into the leading orders and families being already well marked, e.g.
The existing genera include Anas, Aquila, Bubo, Columba, Cypselus, Lanius, Picus, Phalacrocorax, Sula, &c. Very interesting is the fact that Serpentarius, Psittacus and Trogon are amongst this list of birds, which are now restricted to the tropics.
In Colorado and New Mexico Marsh has detected bones of Meleagris, Puffinus, Sula and Uria, all existing genera; but the first is especially suggestive, since it is one of the most characteristic forms of the New World.Advertisement
New Zealand has also yielded many flightless birds, notably the numerous species and genera of Dinornithidae, some of which survived into the 19th century; Pseudapteryx allied to the Kiwi; Cnemiornis, a big, flightless goose; Aptornis and Notornis, flightless rails; and Harpagornis, a truly gigantic bird of prey with tremendous wings and talons.
The numbers of genera and species of birds are, of course, a matter of personal inclination.
The faunas of the two are as absolutely distinct as those of South America and Africa, and it is only because they are separated by a narrow strait instead of the broad Atlantic that they have become so slightly connected by the interchange of a few species and genera.
All the existing Ratitae (with the exception of the ostriches of Africa and South America, belonging to the genera Struthio and Rhea, and comprising at most but five species) are found in Austrogaea and nowhere else.
Of the Meliphagidae the genera Prosthemadera, Pogonornis and Anthornis are peculiar.Advertisement
The continent, however, possesses the two important genera of the Pseudoscines, namely the lyre-birds (Menura) and the scrub-birds (Atrichia).
First in point of importance comes the extraordinarily beautiful family of humming-birds (Trochilidae), with nearly 150 genera (of which only three occur in the Nearctic region) and more than 400 species.
To these follow the tanagers (Tanagridae), with upwards of forty genera (only one of which crosses the border), and about 300 species; the piculules (Dendrocolaptidae), with as many genera, and over 200 species; the ant-thrushes, (Formicariidae), with more than thirty genera, and nearly 200 species; together with other groups which, if not so large as those just named, are yet just as well defined, and possibly more significant, namely, the tapaculos (Pteroptochidae), the toucans (Rhamphastidae), the jacamars (Galbulidae), the motmots (Monotidae), the todies (Todidae), the trumpeters (Psophiidae), and the screamers (Palamedeidae); besides such isolated forms as the seriema (Cariama), and the sun-bittern (Eurypyga).
We note the absence of Ratitae, Tinami, Cracidae, Rhamphastidae, and any of those gruiform genera which are so, characteristic of the continent.
The entire number of Palaearctic families are, according to Newton, 67, and of the genera 323.Advertisement
To compare the Palaearctic genera with those of the Australian and Neotropical regions would be simply a waste of time, for the points of resemblance are extremely few, and such as they are they lead to nothing.
Struthio in Africa and Arabia, fossil also in the Sivalik Hills, and Aepyornithidae in Madagascar; Pittzdae, Bucerotinae and Upupinae, of which Upupa itself in India, Madagascar and Africa; Coraciidae; Pycnonotidae or bulbuls; Trogonidae, of which the Asiatic genera are the less specialized in opposition to the Neotropical forms; Vulturidae; Leptoptilus, Anastomus and Ciconia among the storks; Pteroclidae; Treroninae among pigeons.
Between fifty and sixty so-called families of land birds alone are found within its limits, and of them at least nine are peculiar; the typical genera of which are Buphaga, Euryceros, Philepitta, Musophaga, Irrisor, Leptosoma, Colius, Serpentarius, Struthio, Aepyornis.
Lastly must be noted the extinct tall Ratite species of Aepyornis with its several fancy genera.
We have homely genera, even among the true Passeres, occurring there - such as Alauda, Acrocephalus, Motacilla and Pratincola, while the Cisticola madagascariensis is only distinguishable from the well-known fan-tailed warbler, C. schoenicola of Europe, Africa and India by its rather darker coloration.Advertisement
The Indian or Cisgangetic province is the least rich of the three so far as peculiar genera are concerned.
The Malayan province comprising the Malay islands, besides the Malay peninsula, and the very remarkable Philippines, possess an extraordinary number of peculiar and interesting genera.
In America the name of dace is also applied to members of other genera of the family; the "horned dace" (Semnotilus atromaculatus) is a well-known variety.
As regards invertebrates, very few species or genera are peculiar to Liberia so far as is yet known, though there are probably one or two butterflies of local range.
A large number of beetles inhabit the deep limestone caves of Europe and North America, while many genera and some whole families are at home nowhere but in ants' nests.
It is remarkable that these organs are found in similar positions in genera belonging to widely divergent families, while two genera of the same family may have them in different positions.
Coming to the Tertiary we find the Oligocene beds of Aix, of east Prussia (amber) and of Colorado, and the Miocene of Bavaria, especially rich in remains of beetles, most of which can be referred to existing genera.
In many genera of Lampyridae the female can fly as well as the male; among these are the South European "fireflies."
Other genera of the family are parasitic on Hemiptera - bugs and frog-hoppers - but nothing is known as to the details of their life-history.
Many instances of exaggerated and apparently unnatural structure nevertheless occur, as in the case of the genera Pangonia, Nemestrina, Achias, Diopsis and the family Celyphidae, .and, as might be expected, it is chiefly in tropical species that these peculiarities are found.
Further, while among wasps and bees we find some solitary and some social genera, the ants as a family are social, though some FIG.
C. McCook in the American genus Myrmecocystus, and by later observers in Australian and African species of Plagiolepis and allied genera.
In these ants the difference between the large, heavy, winged males and females, and the small, long-legged, active workers, is so great, that various forms of the same species have been often referred to distinct genera; in Eciton, for example, the female has a single petiolate abdominal segment, the worker two.
Other genera of South American ants - A pterostigma and Cyphomyrmex - make similar fungal cultivations, but they use wood, grain or dung as the substratum instead of leaf fragments.
Moreover, the pollen, instead of consisting of separate cells or grains, consists of cells aggregated into "pollen-masses," the number varying in different genera, but very generally two, four, or eight, and in many of the genera provided at the base with a strap-shaped stalk or "caudicle" ending in a flattish gland or "viscid disk" like a boy's sucker.
In some cases, as in Catasetum, male flowers are produced so different from the female that before the different flowers had been found on the same pike, and before the facts of the case were fully known, they were taken to be representatives of distinct genera.
The number of species of orchids is greater than that of any other monocotyledonous order - not even excepting grasses - amounting to 6000, contained in 400 genera.
It contains two small genera of tropical Asia and Africa with almost regular flowers, and the large genus Cypripedium containing about 80 species in the north-temperate zone and tropical Asia and America.
In Cypripedium two stamens are present, one on each side of the column instead of one only at the top, as in the group Monandreae, to which belong the remaining genera in which also only two stigmas are fertile.
Also some genera mainly represented in South and tropical Africa, such as Satyrium, Disa and others.
Coelogyninae, 7 genera, mostly epiphytes, and inhabitants of tropical Asia.
Pleurothallidinae, characterized by a thin stem bearing one leaf which separates at a distinct joint; the sepals are usually much larger than the petals and lip. Includes To genera, natives of tropical America, one of which, Pleurothallis, contains about 400 species.
Laeliinae, with 22 genera, natives of the warmer parts of America, including three of those best known in cultivation, Epidendrum, Cattleya and Laelia.
Phajinae, includes 15 genera chiefly tropical Asiatic, some- Phajus and Calanthe - spreading northwards into China and Japan.
Cystopodiinae, includes 9 genera tropical, but extending into north temperate Asia and South Africa; Eulophia and Lissochilus 'are ' important African genera.
Catasetinae, with three tropical American genera, two of which, Cataselurn and Cycnoches, have dior tri-morphic flowers.
Dendrobiinae, with six genera in the warmer parts of the Old World; the chief is Dendrobium, with 300 species, often with showy flowers.
The flora of the whole of northern Asia is in essentials the same as that of northern Europe, the differences being due rather to variations of species than of genera.
The genera common to the Himalaya and Europe are much more abundant, and extend throughout the chain, and to all elevations.
Many true Siberian species are found, and more Siberian genera.
A distinct connexion between the flora of the peninsula and Ceylon and that of eastern tropical Africa is observable not only in the great similarity of many of the more truly tropical forms, and the identity of families and genera found in both regions, but in a more remarkable manner in the likeness of the mountain flora of this part of Africa to that of the peninsula, in which several species occur believed to be identical with Abyssinian forms. This connexion is further established by the absence from both areas of oaks, conifers and cycads, which, as regards the first two families, is a remarkable feature of the flora of the peninsula and Ceylon, as the mountains rise to elevations in which both of them are abundant to the north and east.
The number of families relative to the area is very small, and the number of genera and species equally restricted, in very many cases a single species being the only representative of an order.
In the spring there is an abundant herbaceous vegetation, including many bulbous plants, with genera, if not species, identical with those of the Syrian region, some of which extend to the Himalaya.
On the other islands similar characteristics are to be observed, Australian genera extending to the Philippines, and even to southern China.
The mammal fauna of the Indian region of Asia is much more highly developed than that of the Palaearctic. The Quadrumana are represented by several peculiar genera, amongst which are Semnopithecus, Hylobates and Simia.
In the order of Rodents squirrels are very numerous, and porcupines of two genera are met with.
Nearly every order, except that of the Struthiones or ostriches, is well represented, and there are many peculiar genera not found elsewhere, such as Buceros, Harpactes, Lophophorus, Euplocamus, Pavo and Ceriornis.
The Phasianidae (exclusive of true Phasianus) are highly characteristic of this region, as are likewise certain genera of barbets (Megalaeraa), parrots (Palaeornis), and crows (Dendrocitta, Urocissa and Cissa).
In'the birds, the Ethiopian type is shown by the prevalence of larks and' ",stone-chats, and by the complete absence of the many peculiar genera of the Indian region.
Other allied genera are abundant, and extend from the Indian seas to eastern Africa.
The Mullidae, or red mullets, are largely represented by genera differing from those of Europe.
The connexion with Africa is marked by the occurrence of many genera common to Africa and India, and confined to those two regions, and similarities of form are not uncommon there in cases in which the genera are not peculiar.
Though the paired arrangement of the nephridia is the prevalent one in the Chaetopoda, there are many examples, among the Oligochaeta, of species and genera in which there are several, even many, nephridia in each segment of the body, which may or may not be connected among themselves, but have in any case separate orifices on to the exterior.
In some genera the setae are in vertical rows, and in certain Capitellidae these rows so nearly meet that an arrangement occurs reminiscent of the continuous circle of setae in the perichaetous Oligochaeta.
Among the Polychaeta the sexual worm is often more marked from the asexual form, so much so that these latter have been placed in different species or even genera.
This latter arrangement characterizes many genera of the family Megascolicidae and one genus (Periscolex) of the Glossoscolicidae.
In the aquatic genera the epidermis comes to consist entirely of glandular cells, which are, however, arranged in a single layer.
A growth both of the funnel, which becomes multicellular, and of the rest of the nephridium produces the adult nephridia of the genera mentioned.
Among the Megascolicidae, however, which in number of genera and species nearly equals the remaining families taken together, another form of the excretory system occurs.
In the genera Pheretima, Megascolex, Dichogaster, &c., each segment contains a large number of nephridia, which, on account of the fact that they are necessarily smaller than the paired nephridia of e.g.
In any case they have been shown in three genera to develop by the growth and splitting into a series of original paired pronephridia.
The prevalent number of testes is one pair in the aquatic genera and two pairs in earthworms. But there are exceptions; thus a species of Lamprodrilus has four pairs of testes.
Spermathecae are generally present in the Oligochaeta and are absent only in comparatively few genera and species.
Among the aquatic Oligochaeta and many earthworms (the families Lumbricidae, Geoscolicidae and a few other genera) the spermathecae are simple structures, as has been described.
In such other genera of the family as have been examined, the true spermatheca has entirely disappeared, and the sac which contains it in Hyperiodrilus alone remains.
Eyes are present, but hardly so complex as in certain genera of Polychaetes.
In the divine intelligence exist exemplars or types of the genera and species of natural objects.
It is the adrectal gland, and in the genera Murex and Purpura secretes a colourless liquid which turns purple upon exposure to the atmosphere, and was used by the ancients as a dye.
This is a groove, the edges of which are raised and ciliated, lying near the branchial plume in the genera which possess that organ, whilst in Firoloida, which has no branchial plume, the osphradium occupies a corresponding position.
In those Euthyneura in which the shell is entirely absent in the adult, it is, except in the three genera Cenia, Runcina and Vaginula, developed in the larva and then falls off.
In Planorbis, which is sinistral (as are a few other genera or exceptional varieties of various Anisopleurous Gastropods).
Nevertheless, the constant increase of our knowledge of insect forms renders classification increasingly difficult, for gaps in the series become filled, and while the number of genera and families increases, the distinctions between these groups become dependent on characters that must seem trivial to the naturalist who is not a specialist.
A remarkable fossil from the Scottish Coal-measures (Lithomantis) had apparently small wing-like structures on the prothorax, and in allied genera small veined outgrowths - like tracheal gills - occurred on the abdominal segments.
Most of the families and a large proportion of the genera of insects are exceedingly widespread, but a study of the genera and species in any of the more important families shows that faunas can be distinguished whose headquarters agree fairly with the regions that have been proposed to express the distribution of the higher vertebrates.
The southern territory held by this fauna is invaded by genera and species distinctly tropical.
The Australian fauna is rich in characteristic and peculiar genera, and New Zealand, while possessing some remarkable insects of its own, lacks entirely several families with an almost world-wide range - for example, the Notodontidae, Lasiocampidae, and other families of Lepidoptera.
After the determination of a number of cosmopolitan insects that may well have been artificially introduced, there remains a large proportion of endemic species - sometimes referable to distinct genera - which suggest a high antiquity for the truly insular faunas.
He took many liberties with the details of Linnaeus's work, but left the classification, at least of the birds, as it was - a few new genera excepted.'
The accompanying letter press is in some places copious, and useful lists of the species of various genera are occasionally subjoined, adding to the definite value of the work, which, forming one volume, was completed in 1869.
Of a very different kind is the next we have to notice, the Prodromus systematis mammalium et avium of Illiger, published at Berlin in 1811, which must in its day have been a valuable little manual, and on many points it may now be consulted to advantage - the characters of the genera being admirably given, and good explanatory lists of the technical terms of ornithology furnished.
In 1827 Wagler brought out the first part of a Systema avium, in this form never completed, consisting of forty-nine detached monographs of as many genera, the species of which are most elaborately described.
British Museum, began with A List of the Genera of Birds Gray.
In 1855 Gray brought out, as one of the Museum publications, A Catalogue of the Genera and Subgenera of Birds, a handy little volume, naturally founded on the larger works.
The same deficiency became still more apparent when, between 1869 and 1871, he published his Hand-List of Genera and Species of Birds in three 1813-1814, p. xxviii.); but, through the derangements of that stormy period, the order was never carried out (Mem.
To some of the Linnaean genera he dare not, however, assign a place, for instance, Buceros, Haematopus, Merops, Glareola (B risson's genus, by the by) and Palamedea.
Then a new order " Picariae " is instituted for the reception of the Macrochires, Cuculinae, Picinae Psittacinae and Amphibolae of his old arrangement, to which are added three 3 others - Caprimulginae, Todidae and Lipoglossae - the last consisting of the genera Buceros, Upupa and Alcedo.
Instead of recognizing, as before, a subclass in the Ratitae of Merrem, Nitzsch now reduced them to the rank of an order under the name " Platysternae," placing them between the " Gallinaceae " and " Grallae," though admitting that in their pterylosis they differ from all other birds, in ways that he is at great pains to describe, in each of the four genera examined by him - Struthio, Rhea, Dromaeus and Casuarius.
For 5 Not literally, because a few other forms such as the genera Polioptila and Ptilogonys, now known to have no relation to the Tyrannidae, were included, though these forms, it would seem, had never been dissected by him.
At any rate he wavered in his estimate of their taxonomic value, for he gave an alternative proposal, arranging all the genera in a single series, a proceeding in those days thought not only defensible and possible, but desirable or even requisite, though now utterly abandoned.
Next he places the parrots (q.v.), and then the vast assemblage of " Passereaux "- which he declares to be all of one type, even genera like Pipra (manakin, q.v.) and Pitta - and concludes with the somewhat heterogeneous conglomeration of forms, beginning with Cypselus (swift, q.v.), that so many systematists have been accustomed to call Picariae, though to them as a group he assigns no name.
Herein remains, attributed to no fewer than a score of species, which were referred to eight different genera, are fully described and sufficiently illustrated, and, instead of the ordinal name Ichthyornithes previously used, that of Odontotormae was proposed.
Next stands the order Gallinae with 4 " cohorts "; (I) Tetraonomorphae, comprising 2 families, the sand-grouse (Pterocles) and the grouse proper, among which the Central American Oreophasis finds itself; (2) Phasianomorphae, with 4 families, pheasants peacocks, turkeys, guinea fowls, partridges, quails, and hemipodes (Turnix); (3) Macronyches, the megapodes, with 2 families; (4) the Duodecimpennatae, the curassows and guans, also with 2 families; (5) the Struthioniformes, composed of the tinamous; and (6) the Subgrallatores with 2 families, one consisting of the curious South American genera Thinocorus and Attagis and the other of the sheathbill (Chionis).
The controversy between nominalists and realists arose from a passage in Boethius' translation of Porphyry's Introduction to the Categories of Aristotle, which propounded the problem of genera and species, (1) as to whether they subsist in themselves or only in the mind; (2) whether, if subsistent, they are corporeal or incorporeal; and (3) whether separated from sensible things or placed in them.
Perfect orbicular webs are made by many genera of Argyopidae (Zilla, Meta, Gasteracantha), the best-known example being that of the common garden spider of England, Aranea or Epeira diademata; but these webs are not associated with any tubular retreat except such as are made under an adjoining leaf or in some nook hard by.
Cases of parthenogenetic reproduction, or reproduction without the intervention of the male, have been recorded in the case of two genera (Filistata and Tegenaria), and may be commoner than is usually supposed.
The nature of the integument and its hairy clothing in all spiders enables them to be plunged under water and withdrawn perfectly dry, and many species, even as large as the common English house-spider (Tegenaria), are so lightly built that they can run with speed over the surface of standing water, and this faculty has been perfected in genera like Pirata, Dolomedes and Triclaria, which are always found in the vicinity of lakes or on the edges of rivers and streams, readily taking to the water or running down the stems of water plants beneath its surface when pursued.
Remains of spiders from the Baltic amber beds of Oligocene age and from nearly coeval fluviatile or lacustrine deposits of North America belong to forms identical with or closely related to existing genera, thus proving the great antiquity of our present spider fauna.
One of the genera was named Nemertes by Cuvier.
This aggressive character has a different aspect in several genera which are destitute of a central stylet, but in which the surface that is turned outwards upon eversion of the proboscis is largely pro- P. vided with nematocysts, sending the urticating rods of different sizes in all directions.
On the other hand, they are much less considerably or even insignificantly so in the genera that are known to make a rather sparing use of their proboscis.
One of them is found in the two most primitively organized genera, Carinella and Cephalothrix, i.e.
The situation of the lateral nervestems in the different genera with respect to the muscular layers lends definite support to the interpretation of their homologies here given and forms the basis of Burger's classification.
The vessels in the more highly developed genera seem to be partly lacunae and partly true vessels with definite walls.
Archiv fiir Zoologie, ii.; Id., " The Genera of European Nemerteans critically revised," Notes from the Leyden Museum (1879); Id., " Zur Anatomie u.
As ancestors of the Artiodactyle section of the Ungulata, we may look to forms more or less closely related to the North American Lower Eocene genera Mioclaenus and Pantolestes, respectively typifying the families Mioclaenidae and Pantolestidae.
A third type of Condylarthra from the North American Lower Eocene is represented by the family Meniscotheriidae, including the genera Meniscotherium and Hyracops.
Paludina and Bithynia are both British genera.
It had already been understood that the various genera of the Ratitae were the representatives of so many different groups, each of which was at least equivalent to ordinal rank, and that therefore, if the Ratitae were still to be considered a natural group, this common ancestry must be referred to a remote geological epoch.
A departure from the usual regular corolla occurs in Echium and a few allied genera, where it is oblique; in Lycopsis it is also bent.
In most genera the fruit consists of oneseeded nutlets, generally four, but one or more may be undeveloped.
The order is widely spread in temperate and tropical regions, and contains 85 genera with about 1200 species.
In nonflowering plants the works usually followed are for ferns, Hooker and Baker's Synopsis filicum; for mosses, Muller's Synopsis muscorum frondosorum, Jaeger & Sauerbeck's Genera et species muscorum, and Engler & Prantl's Pflanzenfamilien; for algae, de Toni's Sylloge algarum; for hepaticae, Gottsche, Lindenberg and Nees ab Esenbeck's Synopsis hepaticarum, supplemented by Stephani's Species hepaticarum; for fungi, Saccardo's Sylloge fungorum, and for mycetozoa Lister's monograph of the group. For the members of large genera, e.g.
The ordinary systematic arrangement possesses the great advantage, in the case of large genera, of readily indicating the affinities of any particular specimen with the forms most nearly allied to it.
Considerable difference of opinion exists with regard to the best classification of the family, some authorities including most of the species in the typical genus Rhinoceros, while others recognize quite a number of sub-families and still more genera.
Of the " percoideos " there are many genera.
In some few genera of very low type it appears probable that, at any rate in the female, this final change is never effected and that the creature dies a sub-imago.
The number of described species is less than 200, spread over many genera.
Cruciferae is a large order containing nearly 200 genera and about 1200 species.
The insect fauna is very similar to that of Russia; but a few genera, as the Tentyria, do not penetrate into the steppe region of West Siberia, while the tropical Colasposoma, Popilia and Languria are found only in south-eastern Transbaikalia, or are confined to the southern Amur.
On the other hand, several American genera (Cephalaon, Ophryastes) extend into the north-eastern parts of Siberia.'
The ventral valve is usually the larger, and in many genera, such as Terebratula and Rhynchonella, has a prominent beak or umbo, with a circular or otherwise shaped foramen at or near its extremity, partly bounded by one or two plates, termed a deltidium.
The interior of the shell varies very much according to families and genera.
In addition to these, there exists in the interior of the dorsal valve of some genera a variously modified, thin, calcified, ribbon-shaped skeleton for the support of the ciliated arms, and the form of this ribbon serves as one of the chief generic characters of both recent and extinct forms. This brachial skeleton is more developed in some genera than in others.
In the Rhynchonellidae there are two short slender curved laminae, while in many genera and even families, such as the Productidae, Strophomenidae, Lingulidae, Discinidae, &c., there exists no calcified support for the labial appendages.
The ventral valve in many of the genera is provided with two curved hinge-teeth, which fit into corresponding sockets in the opposite valve, so that the valves cannot be separated without breaking one of the teeth.
This cavity lodges the arms, which are curved and coiled in different ways in different genera.
In Terebratulina, Rhyn- chonella, Lingula, and possibly other genera, the arms can be unrolled and protruded from the opened shell; in this case the tentacles also FIG.
The latter pair alone persists in all other genera.
The number and position of the muscles differ materially in the two great divisions into which the Brachiopoda have been grouped, and to some extent also in the different genera of which each division is composed.
Such is the general arrangement of the shell muscles in the division composing the articulated Brachiopoda, making allowance for certain unimportant modifications observable in the animals composing the different families and genera thereof.
The form of the deltidium varies in different genera.
As a rule the genera of the northern hemisphere differ from those of the southern.
In the bibliography at the close of this article (referred to by leaded arabic numerals in brackets throughout these pages), the titles of works are given which contain detailed information as to the genera and species of each order or sub-order, their geographical distribution and their habits and economy so far as they have been ascertained.
Some large species of peculiar genera are taken at great depths.
The genera Belinurus, Aglaspis, Prestwichia, Hemiaspis and Bunodes consist of small forms which occur in Palaeozoic rocks.
At the present day scorpions of various genera are found in all the warm regions of the world.
The best-known genera were Anthracomartus and Eophognus.
Several genera have been established, the best-characterized being Geraphognus and Architarbus.
Liliaceae is one of the larger orders of flowering plants containing about 2500 species in zoo genera; it is of world-wide distribution.
It contains 36 genera, many of which are north temperate and three are represented in Britain, viz.
It contains 64 genera.
A small group of Australian genera closely approach the order Juncaceae in having small crowded flowers with a scarious or membranous perianth; they include Xanthorrhoea (grass-tree or blackboy) and Kingia, arborescent plants with an erect woody stem crowned with a tuft of long stiff narrow leaves, from the centre of which rises a tall dense flower spike or a number of stalked flower-heads; this group has been included in Juncaceae, from which it is doubtfully distinguished only by the absence of the long twisted stigmas which characterize the true rushes.
It contains 28 genera, several being represented in Britain.
To this group belong a number of tropical and especially South African genera such as Albuca, Urginea, Drimia, Lachenalia and others.
Yucca and several allied genera are natives of the dry country of the southern and western United States and of Central America.
They contain a few genera chiefly old world tropical and subtropical.
It resembles Juncaceae in the general plan of the flower, which, however, has become much more elaborate and varied in the form and colour of its perianth in association with transmission of pollen by insect agency; a link between the two orders is found in the group of Australian genera referred to above under Asphodeloideae.
The indigenous fauna of Brazil is noteworthy not only for the variety and number of its genera and species, but also for its deficiency in the larger mammals.
Of the Muridae there are several genera and a large number of species, some of them evidently importations from the Old World.
The avifauna of Brazil is rich in genera, species and individuals, especially in species with brilliantly-coloured plumage.
The reptilian fauna exhibits an exceptionally large number of interesting genera and species.
Most prominent among these is the American alligator, of which there are, according to Netterer, two genera and eight species in Brazil.
The batrachians include a very large number of genera and species, especially in the Amazon valley.
The chief characteristic of the Amazonian forest, aside from its magnitude, is the great diversity of genera and species.
He concludes that the genera and species exist as universals only in thought; but, inasmuch as they are collected from singulars on account of a real resemblance, they have a certain existence independently of the mind, but not an existence disjoined from the singulars of sense.
But, since those universals, so far as they are called genera and species, cannot be perceived by any one in their purity without the admixture of imagination, Plato maintained that they existed and could be beheld beyond the things of sense, to wit, in the divine mind.
The most interesting part of the work is the distinction which Gilbert draws between the manner of existence of genera and species and of substances proper.
Genera and species certainly exist, but they do not exist in their own right as substances.
As against Realism he maintains consistently Res de re non praedicatur; genera and species, therefore, which are predicated of the individual subject, cannot be treated as things or substances.
Albert and Aquinas both profess the moderate Aristotelian Realism which treats genera and species only as substantiae secundae, yet as really inherent in the individuals, and constituting their form or essence.
It contains about 40 genera with more than 1000 species, and is found in all parts of the world except the coldest, but is especially well developed in tropical Asia and tropical America.
In hot dry districts such as Arabia and north-east tropical Africa, genera have been developed with a low, much-branched, dense, shrubby habit, with small hairy leaves and very small flowers.
The sepals, which are generally free, show much variation in size, shape and covering, and afford valuable characters for the distinction of genera or sub-genera.
The style is simple or branched, and the stigma is linear, capitate or globose in form; these variations afford means for distinguishing the different genera.
The number of genera recognized by Lamarck is more than ten times as great as that recorded by Linnaeus.
The whole " system " or scheme of classification was termed a genealogical tree (Stammbaum); the main branches were termed " phyla," their branchings " sub-phyla "; the great branches of the sub-phyla were termed " cladi," and the " cladi " divided into " classes," these into sub-classes, these into legions, legions into orders, orders into sub-orders, suborders into tribes, tribes into families, families into genera, genera into species.
The terms used for indicating groups are " Phylum " for the large diverging branches of the genealogical tree as introduced by Haeckel, each Phylum bears secondary branches which are termed " classes," classes again branch or divide into orders, orders into families, families into genera, genera into species.
There are six species of monkey corresponding to those of Guiana and the Amazon valley, the sloth and ant-eater, 12 known genera of rodents, including many species of Mures, the cavy, the capybara, the paca, the nutria, the agouti, the tree porcupine, Loncheres cristata, Echimys cayen and the Brazilian hare.
Bird life is represented chiefly by migratory species, particularly of genera that inhabit the shores of streams and lagoons.
Insect life is perhaps poorer and less varied than in Brazil, but in the 14 orders of insects there are no less than 98 families, each including many genera and species.
They inhabit chiefly the northern seas, but many abyssal forms occur between the tropics and in the southern parts of the Atlantic and Pacific. They are represented in British waters by eight genera, and about twenty species, only one of which, the burbot (Lola vulgaris), is an inhabitant of fresh waters.
It is well represented in Britain by the two genera which comprise nearly the whole order - Juncus, rush, and Luzula, woodrush.
The number of genera is few.
The bird-lice (Mallophaga) are far more numerous in species, although the number of genera is comparatively small.
The Megatheriidae, which include a number of genera, are collectively Megatherium, from the specimen in the Museum of the Royal College of Surgeons of England.
The two genera agree closely in form and structure and may possibly belong to the cycle of the same or of allied species.
In a few genera the place of the chitinoid coat is taken by a ciliary investment and in most families the structure of the layers is characteristic.
In some genera a " urocyst " is formed, the tail of which gives rise to a new cyst and a fresh scolex.
The most remarkable feature of this cystic development is the formation in many genera of several internal buds within a common cyst, each of which forms an independent inverted scolex (Coenurus, Polycercus); or these internal vesicles may bud off a large number of scolices on their external surface (Staphylocystis).
The terminal or first-formed proglottis is sterile, and contains the primitive and (except in a few genera) the only excretory pore.
The Bovidae comprise a great number of genera and species, and include the oxen, sheep, goats, antelopes and certain other kinds which come under neither of these designations.
The present family doubtless originated in the northern half of the Old World, whence .it effected an entrance by way of the Bering Strait route into North America, where it has always been but poorly represented in the matter of genera and species.
The genera are Ovis (sheep), Capra (goats) and Hemitragus (tahr).
Next come the Rupicaprinae, which include several genera of mountain-dwelling ruminants, typified by the European chamois (Rupicapra); the other genera being the Asiatic serow, goral and takin, and the North American Rocky Mountain goat.
The Forficulidae are almost cosmopolitan; but the various species and genera differ from each other both in structure and size to a comparatively slight extent.
Before the year 1899 mosquitoes had never been collected systematically, and had received little notice from entomologists, so that but few genera and comparatively few species were known.
Nearly zoo genera and about 700 species of mosquitoes are now recognized, but in all probability the total number of species is not less than 1000.
In dividing the Culicidae into genera reliance is placed chiefly upon characters derived from the scales on the three divisions of the body and on the wings.
The old genus Anopheles (characterized by the palpi being long in both sexes) is now divided into a number of genera according to the character and shape of the scales on the different regions of the body and on the wings.
These genera make up the sub-family Anophelinae, and together include over ioo species.
The name cedar is applied to a variety of trees, including species of several genera of Conifers, Juniperus, Thuja, Libocedrus and Cupressus.
The former is specially modified in a few genera in a manner analogous to the "proboscis" of certain Rhabdocoel Turbellaria.
Both male and female gonoducts open through acornmon atrium to the exterior by tkis pore, but in three bisexual genera the male and female ducts are developed in separate individuals (Bilharzia, Didymozoon, Koellikeria).
The Cyclostomata are numerous in Palaeozoic rocks, but attained a specially predominant position in the Cretaceous strata, where they are represented by a prpfusion of genera and species; while they still survive in considerable numbers at the present day.
They are the dominant group at the present day, and are represented by a large number of genera and species.
In the encrusting type, which is found in a large proportion of the genera, the zooids are usually in a single layer, with their orifices facing away from the substratum; but in certain species the colony becomes multilaminar by the continued superposition of new zooids over the free surfaces of the older ones, whose orifices they naturally occlude.
The rigid Cheilostomes which have this habit were formerly placed in the genus Eschara, but the bilaminar type is common to a number of genera, and there can be no doubt that it is not in itself an indication of affinity.
This habit is characteristic of the genera Crisia, Cellaria, Catenicella and others, while it occurs in certain species of other genera.
As indications that the conditions described in Membranipora and Cribrilina are of special significance may be noted the fact that the ancestrula of many genera which have well-developed compensation-sacs in the rest of their zooecia is a Membranipora-like individual with a series of marginal calcareous spines, and the further fact that a considerable proportion of the Cretaceous Cheilostomes belong either to the Membraniporidae or to the Cribrilinidae.
In the so-called Selenariidae, probably an unnatural association of genera which have assumed a free discoidal form of zoarium, they may reach a very high degree of development, but Busk's suggestion that in this group they "may be subservient to locomotion" needs verification.
The Boidae comprise some 60 species, which have been grouped into many fancy genera.
Many of the so-called genera, or groups of genera, are consequently not to be used either as witnesses of blood-relationship or of geographical distribution.
It is impossible here to mention any but the more obvious genera and groups of colubrine snakes.
Only a few out of the more than 120 genera can be mentioned here.
Dipsadomorphus, Dipsas, Leptognathus, Dryophis, Dendrophis and other closely allied genera are typical, very long-bodied and longtailed tree-snakes, chiefly tropical.
About 30 species, with several genera, are known from the oriental and neotropical regions.
Absolutely restricted to the Old VL orld, with 9 genera comprising about 40 species.
While the imaginative and emotional side of Roman poetry was so powerfully represented by Lucretius, attention was directed to its artistic side by a younger genera tion, who moulded themselves in a great degree on Alexandrian models.
In other genera the leaves are much divided and sometimes very large; those of Dracontium (tropical America) may be 15 ft.
Campodea Machilis and Lepisma - to which belongs the "silverfish" (q.v.) - are the best known genera.
Few genera have greater claims to notice from an economic point of view.
Members of the closely allied genera Gasteria and Haworthia, with a similar mode of growth, are also cultivated and popularly known as aloes.
As applied by Linnaeus, the name Cactus is almost conterminous with what is now regarded as the natural order Cactaceae, which embraces several modern genera.
The principal modern genera are grouped by the differences in the flower - tube just explained.
Those with long - tubed flowers comprise the genera Melocactus, Mammillaria, Echinocactus, Cereus, Pilocereus, Echinopsis, Phyllocactus, Epiphyllum, &c.; while those with short-tubed flowers are Rhipsalis, Opuntia, Peireskia, and one or two of minor importance.
The margins of these leaf-like branches are more or less crenately notched, the notches representing buds, as do the spine-clusters in the spiny genera; and from these crenatures the large showy flowers are produced.
The trochanter is simple in some genera and divided in others.
The " fig-insects," whose presence in ripening figs is believed essential to the proper development of the fruit, belong to Blastophaga and other genera of this family.
The habit of some genera is to catch the prey before making their tunnel, but more frequently the insect digs her nest, and then hunts for prey to put into it.
The " tongue," for example, is short and obtuse or emarginate in Colletes and Prosopis, while in all other bees it is pointed at the tip. But in Andrena and its allies it is comparatively short, while in the higher genera, such as A pis and Bombus, it is elongate and flexible, forming a most elaborate and perfect organ for taking liquid food.
Most of the genera are " solitary " in habit, the female sex being undifferentiated; but among the humble-bees and hive-bees we find, as in social wasps and ants, the occurrence of workers, and the consequent elaboration of a wonderful insect-society.
Both Heteropterous and Homopterous genera have been described from the Carboniferous, but the true nature of some of these is doubtful.
The Pentatomidae (shield bugs), some of which are metallic or otherwise brightly coloured, are easily recognized by the great development of the scutellum, which reaches at least half-way back towards the tip of the abdomen, and in some genera covers the whole of the hind body, and also the wings when these are closed.
In the Coccids the forma tion of a protective waxy secretion - present in many genera of Homoptera - reaches its most extreme development.
Allied genera are Diplobune and Dacrytherium.
The most interesting genera are, however, the Upper Oligocene and Lower Miocene Gelocus and Prodremotherium, which have perfectly selenodont teeth, and the third and fourth metacarpal and metatarsal bones respectively fused into an imperfect cannon-bone, with the reduction of the lateral metacarpals and metatarsals to mere remnants of their upper and lower extremities.
In the above genera, so far as is known, the feet were four-toed, although with the lateral digits relatively small; but in Elotherium (or Entelodon), from the Lower Miocene of Europe and the Oligocene of North America, the two lateral digits in each foot had disappeared.
Of the various other genera allied to Mimus, the best known are the thrashers (genus Harporhynchus) of which six or eight species are found in North America, which are thrush-like and shy in their habits and do not mimic; and the cat-bird (Galeoscoptes carolinensis), which in addition to having an attractive song, utters clucks, whistles and mewing sounds.
For the characteristics of the family Sciuridae and the different squirrel-like genera by which it is represented, see Rodentia.
The birds are more West African than the mammals, and include the grey parrot, all the genera of the splendidly-coloured turacoes, the unique " whale-headed stork," and the ostrich.
Among the latter two genera, Distaechurus and Dorcopsis, are peculiar.
The most recent lists record over 500 species as found in the Papuan area, and of these between 50 and 60 genera are peculiar to it.
Only 4 genera and 5 species of snakes are peculiar to New Guinea, many of them poisonous.
All the above genera differ from Megatherium in having a foramen on the inner side of the lower end of the humerus.
Several genera and species of Tardigrada have been described, perhaps the best known being Macrobiotus schultzii and Milnesium tardigradum.
Gadow has more recently treated of this family, reducing the number of both genera and species, though adding a new genus discovered since the publication of Shelley's work.
The Neotraginae (or Nanotraginae) form an exclusively African group of small-sized antelopes divided into several, for the most part nearly related, genera.
Allied to the lapwing are several forms that have been placed by ornithologists in the genera Hoplopterus, Chettusia, Lobivanellus, Defilippia.
The flora is most closely associated with that of New Zealand, and the avifauna indicates the same connexion rather than one with Australia, as those birds which belong to Australian genera are apparently immigrants, while those which occur on the island in common with New Zealand would be incapable of such distant migration.
Of all sea-fishes Clupeae are the most abundant; for although other genera may comprise a greater variety of species, they are far surpassed by Clupea with regard to the number of individuals.
His Genera Plantarum, begun in 1778, and finally published in 1789, was an important advance, and formed the basis of all natural classifications.
The work was continued after his death, by his son Alphonse de Candolle, with the aid of other eminent botanists, and embraces descriptions of the genera and species of the orders of Dicotyledonous plants.
The word "lily" is loosely used in connexion with many plants which are not really liliums at all, but belong to genera which are Madonna or White Lily (Lilium candidum).
Their galls are to be met with on a great variety of plants of widely distinct genera, e.g.
Thus the galls of Cynips and its allies are inhabited by members of other cynipideous genera, as Synergus, Amblynotus and Synophrus; and the pine-cone-like gall of Salix strobiloides, as Walsh has shown, 2 is made by a large species of Cecidomyia, which inhabits the heart of the mass, the numerous smaller cecidomyidous larvae in its outer part being mere inquilines.
A good example of this is seen in two common genera of British hydroids, Cordylophora and Tabularia.
He makes 9 families of the group, and recognizes 45 genera, and 442 species, besides subspecies.
About 80 genera with more than 500 species are recognized, divided into the family Psittacidae with the subfamilies Stringopinae, Psittacinae and Cacatuinae, and the family Trichoglossidae with the subfamilies Cyclopsittacinae, Loriinae and Nestorinae.
Of the three genera Hystrix is characterized by the inflated skull, in which the nasal chamber is often considerably larger than the brain-case, and The Porcupine (Hystrix cristata).
They include three genera, of which the first is represented by the Canadian porcupine (Erethizon dorsatus), a stout, heavily-built animal, with long hairs almost or quite hiding its spines, four frontand five hind-toes, and a short, stumpy tail.
Effective pollination may also occur between flowers of different species, or occasionally, as in the case of several orchids, of different genera - this is known as hybridization.
There are also now two more genera, Paranebalia (Claus, 1880), in which the branchial feet are much longer than in Nebalia, and Nebaliopsis (Sars, 1887), in which they are much shorter.
The remaining family, the Branchipodidae, includes eight genera.
Of Branchiopsyllus (Sars, 1897) the male is not yet known, but in his genera of the same date, the Siberian Artemiopsis and the South African Branchipodopsis (1898), there is no such appendage.
The single family Apodidae contains only two genera, Apus and its very near neighbour Lepidurus.
Of the seven genera, the cosmopolitan Daphnia contains about 100 species and varieties, of which Thomas Scott (1899) observes that " scarcely any of the several characters that have at one time or another been selected as affording a means for discriminating between the different forms can be relied on as satisfactory."
This family, so commonly called Lynceidae, contains a large number of genera, among which one may usually search in vain, and rightly so, for the genus Lynceus.
Of its many genera, Leydigia, Leydigiopsis, Monospilus have been already mentioned.
To the Polyphemidae, the wellknown family of the former tribe, Sars in 1897 added two remarkable genera, Cercopagis, meaning " tail with a sling," and Apagis, " without a sling," for seven species from the Sea of Azov.
In some of the genera parthenogenetic propagation is carried to such an extent that of the familiar Cypris it is said, " until quite lately males in this genus were unknown; and up to the present time no male has been found in the British Islands " (Brady and Norman, 1896).
On the other hand, the ejaculatory duct with its verticillate sac in the male of Cypris and other genera is a feature scarcely less remarkable.
The mandibles are normally five-jointed, with remnants of an outer branch on the second joint, the biting edge varying from strong development to evanescence, the terminal joints or " palp " giving the organ a leg-like appearance and function, which disappears in suctorial genera such as Paracytherois.
There is but one family, the Calanidae, but this is a very large one, with 26 genera and more than ioo species.
There are four families, the Diaptomidae with 27 genera, the Pontellidae with to, the Pseudocyclopidae and Candaciidae each with one genus.
To the Cyclopidae six genera are allotted by Giesbrecht in 1900.
Giesbrecht, displacing the older name Ascomyzontidae, assigns to this family 21 genera in five subfamilies, and suggests that the long-known but still puzzling Nicothoe from the gills of the lobster might be placed in an additional subfamily, or be made the representative of a closely related family.
For the distinguishing marks of all these, the number of their genera and species, their habits and transformations and dwellings, the reader must be referred to the writings of specialists.
They are divided into numerous genera and the number of species is very large indeed.
The few genera and species are undoubtedly a heterogeneous assembly, as indicated by their very scattered distribution, but they all agree in their decidedly handsome colour pattern, bands of dark brown to maroon upon a light ground.
The family, comprising some 200 species, with about 30 genera, shows great diversity of form; the terrestrial members are mostly flatbodied, the arboreal more laterally compressed and often with a very long tail.
According to the very varied habits, their external appearance varies within wide limits, there being amongst the 300 species, with 50 genera, arboreal, terrestrial, burrowing and semi-aquatic forms, and even one semi-marine kind.
Sauromalus, Crotaphytus, Callisaurus, Holbrookia, Uma, Uta are typical Sonoran genera, some ranging from Oregon through Mexico.
This large, typically American family comprises more than ioo species which have been arranged in many genera.
Trogonophis, Pachycalamus and Agamodon of Africa are all acrodont; the other genera are pleurodont.
This large family contains about 400 species, with numerous genera; the greatest diversity in numbers and forms occurs in the tropical parts of the Old World, especially in the Australian region, inclusive of many of the Pacific islands.
The few genera and species of this family are restricted to Africa, south of the Sahara.
The Lacertidae or true lizards comprise about 20 genera, with some 1 00 species, most abundant in Africa; their northern limit coincides.
Other genera are Psammodromus and Acanthodactylus in southwestern Europe and northern Africa.
Ortmann has traced the centre of dispersal of the fresh-water Crawfish genera Cambarus, Potamobius and Cambaroides to eastern Asia, where their common ancestors lived in Cretaceous time.
This intermingling of types does not apply to south-eastern Mexico, where animal life is represented by many of the genera and species found in the forested lowlands of the great Amazon basin.
The most numerous, perhaps, are the humming-birds, of which there are many genera and species, each one distinct in form and colour.
The insect fauna of Mexico covers a very wide range of genera and species which, like the other forms of animal life, is largely made up of migratory types.
Spiders are also represented by a large number of genera and species, the most dreaded being the venomous " tarantula " and the savage " mygale."
These widely divergent conditions give to Mexico a flora that includes the genera and species characteristic of nearly all the zones of plant life on the western continents - the tropical jungle of the humid coastal plains with its rare cabinet-woods, dye-woods, lianas and palms; the semi-tropical and temperate mountain slopes where oak forests are to be found and wheat supplants cotton and sugar-cane; and above these the region of pine forests and pasture lands.
Its forests are not composed of one or a few dominating species, as in the cold temperate zone, but of countless genera and species closely interwoven together - a confused mass of giant trees, lianas and epiphytes struggling to reach the sunlight.
This typically consists of two concentric zones, the trochus and cingulum, often separated by a groove or gutter which may be finely ciliated; but in several genera of no close affinity, where it is very oblique to the longitudinal axis of the body, it is represented by a general ciliation of the surface (Taphrocampa, Rattulus, Copeus, Adineta).
Additional paired antennae may occur within the coronal surface, which is the seat of the sensory styles, of less complex structure, which occur in many genera.
Ehrenberg included the Rotifers in his Infusionsthiere, and described and figured with fair precision many of the genera and species.
Such was the structure of the appendages in Trilobites belonging to the genus Triarthrus; but considering the great structural differences that obtain between Triarthrus and many other genera, it would be rash to assume that there were not corresponding differences in the structure of the limbs.
It is probable that no satisfactory classification of the Trilobites will be proposed until the limbs of most of the genera have been examined.
Up to the present time all attempts to arrange the genera in natural and definable groups have failed to meet with general approval; and this criticism must be extended to Beecher's subdivision of the class into three orders, named Hypoparia, Proparia and Opisthoparia, based upon the form and position of a groove, the so-called genal suture, which marks the lateral portion of the head-shield.
Those genera, like Paradoxides, Olenus, Asaphus, Phillipsia and others, in which this groove cuts the posterior edge of the head-shield on the inner side of its angle are referred to the Opisthoparia; those, like Dalmanites and Phacops, in which it cuts the lateral border in front of the posterior angle, belong to the Proparia.
But in certain genera, like Conocoryphe, Calymmene and Triarthrus, it cuts the margin of the head-shield so close to the posterior angle that the distinction between the two groups practically breaks down.