In Clausilia, according to the observations of C. Gegenbaur, the primitive shell-sac does not flatten out and disappear, but takes the form of a flattened closed sac. Within this closed sac a plate of calcareous matter is developed, and after a time the upper wall of the sac disappears, and the calcareous plate continues to grow as the nucleus of the permanent shell.
On the bank of the Tiretaine there is a remarkable calcareous spring, the fountain of St Allyre, the copious deposits of which have formed a curious natural bridge over the stream.
The oak grows most luxuriantly on deep strong clays, calcareous marl or stiff loam, but will flourish in nearly any deep well-drained soil, excepting peat or loose sand; in marshy or moist places the tree may grow well for a time, but the timber is rarely sound; on hard rocky ground and exposed hillsides.
While the rugged and mountainous district of Calabria, extending nearly due south for a distance of more than 150 m., thus derives its character and configuration almost wholly from the range of the Apennines, the long spur-like promontory which projects towards the east to Brindisi and Otranto is merely a continuation of the low tract of Apulia, with a dry calcareous soil of Tertiary origin.
60), where the interspaces between the coenosarcal tubes are filled up with calcareous matter, or coenosteum, replacing the chitinous perisarc. The result is a stony, solid mass, which contributes to the building up of coral reefs.
- Metagenetic colony-forming Hydromedusae, in which the polyp-colony forms a massive, calcareous corallum into which the polyps can be retracted; polyp-individuals always of two kinds, gastrozoids and dactylozoids; gonosome either free medusae or sessile gonophores.
(After coralline may be regarded as a form of Moseley.) hydroid colony in which the coenosarc forms a felt-work ramifying in all planes, and in which the chitinous perisarc is replaced by a massive calcareous skeleton.
- Portion of the calcareous corallum of Millepora nodosa, showing the cyclical arrangement of the pores occupied by the " persons " or hydranths.
Obviously no more than this is possible until physiologists are able to state much more precisely than at present what is the influence of common salt on the plants of salt-marshes, of the action of calcium carbonate on plants of calcareous soils, and of the action of humous compounds on plants of fens and peat moors.
Habitats rich in mineral salts, especially calcium carbonate, poor in acidic humous compounds, and characterized by ash woods, beech woods, and calcareous pasture.
Calcicole and Calcifuge Species.Plants which invariably inhabit calcareous soils are sometimes termed calcicoles; calcifuge species are those which are found rarely or never on such soils.
In England, the following species are confined or almost confined to calcareous soils: A splenium Ruta-muraria, Melica nutans, Carex digitata, Aceras anthropophora, Ophrys ap~ifera, Thalictrum minus, Helianthemum Chamaecislus, Viola hirta, Linum perenne, Geranium lucidum, Hippocrepis comosa, Potentiila verna, Viburnum Lantana, Galium asperum (= G.
Other plants occur indifferently both on calcareous and on non-calcareous soils.
It is sometimes said that lime acts as a poison on some plants and not on others, and sometimes that it is the physiological dryness of calcareous soils that is the important factor.
Again, acidic humus does not form in calcareous soils; and hence one does not expect to find plants characteristic of acidic peat or humus on calcareous soils.
The upper, wide opening of the duct is attached by elastic, peritoneal lamellae to the hinder margin of the left lung; the middle portion of the duct is glandular and thick-walled, for the deposition of the albumen; it is connected by a short, constricted " isthmus " (where the shell-membrane is formed) with a dilated " uterus " in which the egg receives its calcareous shell and eventual pigmentation.
The later beds of the island belong to the Jurassic, Cretaceous and Tertiary systems. At the western foot of the Ida massif calcareous beds with corals, brachiopods (Rhvnchonella inconstans, &c.) have been found, the fossils indicating the horizon of the Kimmeridge clay.
It v e mires very little moisture, grows luxuriantly on the thin calcareous soil of Yucatan and is cultivated almost exclusively by the large landowners.
The Jackson formation south-west of the Lisbon beds, is made up chiefly of grey calcareous clay marls, bluish lignitic clays, green-sand and grey siliceous sands.
Calcareous tufa or travertine occurs in the valley of Matlock and elsewhere, the southern part of the county, from Matlock southward by Heage, Belper and Duffield to Derby.
Calcareous tufa or travertine occurs in the valley of Matlock and elsewhere, and in some places is still being deposited by springs.
Any good free loam is suitable, but a calcareous loam is the best.
Shell semi-globular, with short spire; operculum calcareous, not spiral.
Cyclostoma, shell turbinated, operculum calcareous, British.
Shell conical; foot secreting a ventral calcareous plate; animal fixed.
Cephalic shield short, truncated posteriorly; eyes deeply embedded; three calcareous stomachal plates; shell external, with reduced spire.
It is supposed to act in some way as a stimulant in copulation, but possibly has to do with the calcareous covering of the egg-capsule.
Shell largely chitinous, not spiral, its calcareous apex projecting through a small hole in the mantle.
But it was now made to appear that the struthious birds in this respect resembled, not only the duck, but a great many other groups - waders, birds-of-prey, pigeons, passerines and perhaps all birds not gallinaceous - so that, according to Cuvier's view, the five points of ossification observed in the Gallinae, instead of exhibiting the normal process, exhibited one quite exceptional, and that in all other birds, so far as he had been enabled to investigate the matter, ossification of the sternum began at two points only, situated near the anterior upper margin of the side of the sternum, and gradually crept towards the keel, into which it presently extended; and, though he allowed the appearance of detached portions of calcareous matter at the base of the still cartilaginous keel in ducks at a certain age, he seemed to consider this an individual peculiarity.
The surface of the country is remarkably level, with numerous deep ravines in the calcareous conglomerate.
The soil consists, for the most part, either of clay intermixed with sand or of calcareous earth, and is on the whole fruitful.
Soils are of four classes: calcareous-ferruginous, alluvial, argillous and silicious.
Calcareous lands are predominant, especially in the uplands.
The material is largely calcareous, and has probably been derived from the disintegration of the reefs, and from the shells of animals living in the shallows.
On the south coast of the same island are coarse-grained, brownish micaceous and light-coloured calcareous sandstone and marls, containing fossils, which render it probable that they are of the same age as the coal-bearing Jurassic rocks of Brora (Scotland) and the Middle Dogger of Yorkshire.
Lime is, in fact, absorbed to an enormous extent by fishes, molluscs, crustacea, calcareous algae and sponges, starfishes, sea-urchins and feather stars, many polyzoa and a multitude of protozoa (mainly the foraminifera).
All these animals have calcareous skeletons or shells of some form and they secrete the calcium from its solution as sulphate, converting it into carbonate.
In so far as it depends on solution of calcareous rock the Semper-Murray theory of coral reefs is unsatisfactory.
Dorsal valve, showing calcareous spiral coils.
The outer surfaces of the mantle secrete' the shell, which is of the nature of a cuticle impregnated by calcareous salts.
These canals are closed externally and are absent in Rhynchonella, where the amount of calcareous deposit is small.
Lophophore supported by calcareous loops, &c. [[Families.
Calcification and calcareous deposits are extremely common in many pathological conditions.
The tree succeeds in deep, sandy or calcareous loams, and in stiff loams resting on a gravelly bottom.
It has been sought to work again the ancient quarries of Shemtu, but it was found that the marble had been spoilt by ferruginous and calcareous veins.
Orifice concealed at the bottom of a vestibular shaft, surrounded by a solid or vesicular calcareous deposit.
The Ctenostomata are ill adapted for preservation as fossils, though remains referred to this group have been 1 Calcareous spicules have been described by Lomas in Alcyonidium gelatinosum.
In many calcareous forms, .both Cheilostomes and Cyclostomes, the zoarium is rendered flexible by the interposition of chitinous joints at intervals.
8 A, 9 A), but in many Cheilostomes the frontal surface is protected by a calcareous shield, which grows from near the free edges of the vertical walls and commonly increases in thickness as the zooecium grows older by the activity of the "epitheca," a layer of living tissue outside it.
The evolution of the arrangements for protruding the polypide seems to have proceeded along several distinct lines: (i.) In certain species of Membranipora the "frontal membrane," or membranous free-wall, is protected by a series of calcareous spines, which start from its periphery and arch inwards.
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.
And lateral sides, of a calcareous lamina covered externally by a soft membrane.
Whether the closed primitive shell-sac of the slugs (and with it the transient embryonic shell-gland of all other Mollusca) is precisely the same thing as the closed sac in which the calcareous pen or shell of the Cephalopod Sepia and its allies is formed, is a further question which we shall consider when dealing with the Cephalopoda.
The calcareous Claiborne or ClaiborneLisbon formation-group lies south of the last, in a wedge-like strip with the apex on the Alabama boundary; it is a series of clays and sands, richly fossiliferous.