The carapace of the prosoma was unsegmented and often bore a pair of eyes.
Ad, Muscle from carapace to entosternum.
- Ventral view of the posterior carapace or meso-metasomatic (opisthosomatic) fusion of Limulus polyphemus.
(After Kingsley.) to it from the bases of the surrounding limbs and from the dorsal carapace and from the pharynx.
The general form and structure of their prosomatic carapace are in many striking features identical with that of Limulus.
Intermediate somites forming a mesosoma occur, but tend to fuse superficially with the metasomatic carapace or to become co-ordinated with the somites of the metasoma, whether fused or distinct to form one region, the opisthosoma (abdomen of authors).
The greater or less evolution and specialization of the metasomatic carapace appears to be the most important basis for classification - but this has not been made use of in the latest attempts at drawing up a system of the Trilobites.
Carapace and similar in appearance to the free somites.
This would lead to the supposition that the great development of metasomatic carapace is a primitive and not a late character, were it not for the fact that Paradcxides and Atops, with an inconspicuous telsonic carapace and numerous free somites, are also Cambrian in age, the latter indeed anterior in horizon to Agnostus.
The posterior carapace of the Trilobites and of Limulus is probably enough in origin a telsonic carapace - that is to say, is the tergum of the last segment of the body which carries the anus.
E, Stage with twelve free somites; the telsonic carapace has not increased in size.
Between the bases of the sixth pair cf limbs and behind the prosomatic carapace is seen the tergite of the small prae-genital somite.
- Dorsal plate of prosoma (carapace) narrowed in front; the appendages of the 1st pair small, much narrower, taken together, than the posterior border of the carapace.
- Orifice of foetid glands opening on a tubercle situated near the lateral border of the carapace above the base of the 5th appendage.
Many of the Cambrian trilobites appear to have been blind, and they had not at this period developed that flexibility in the carapace that some forms acquired later.
The carapace, formerly referred only to the antennar-mandibular segments, may perhaps in fact contain elements from any number of other segments of head and trunk, Huxley, Alcock, Bouvier giving support to this opinion by the sutural or other divisional lines in Potamobius, Nephrops, Thalassina, and various fossil genera.
In the family Homolidae stands the strange genus Latreillia, Roux, with long slender limbs and triangular carapace after the fashion of oxyrhynch spider-crabs.
In Homola the carapace is quadrilateral.
Usually the sides of the carapace are strangely produced into a mock rostrum in front of the ocular lobe, be it oculiferous or not.
Sometimes the one partner affords the other merely a convenient means of transport, as in the case of the barnacles which grow on, or of the gulf-weed crab which clings to, the carapace of marine turtles.
C, carapace covering the cephalothorax.
2, Nebalia bipes (one side of 5, Branchipus stagnalis: a, adult carapace removed).
Of the class, is the possession of a carapace or shell, arising as a dorsal fold of the integument from the posterior margin of the head-region.
3), this coalescence affects only the dorsal region of the thoracic somites, and the lateral portions of the carapace overhang on each side, enclosing a pair of chambers within which lie the gills.
Magnified 25 times, showing the orifice of entrance (x) into the cavity overarched by the carapace in which an appendage of the maxilliped (f) plays.
This is partly due to the fact that many important forms must have escaped fossilization altogether owing to their small size and delicate structure, while very many of those actually preserved are known only from the carapace or shell, the limbs being absent or represented only by indecipherable fragments.
It may be supposed to have approximated, in general form, to A pus, with an elongated body composed of numerous similar somites and terminating in a caudal furca; with the post-oral appendages all similar and all bearing gnathobasic processes; and with a carapace originating as a shell-fold from the maxillary somite.
Owen to the typical representative of a group of gigantic, armadillo-like, South American, extinct Edentata, characterized by having the carapace composed of a solid piece (formed by the union of a multitude of bony dermal plates) without any movable rings.
In some specimens of these genera the horny shields covering the bony scutes of the carapace have been preserved, and since the foramina, which often pierce the latter, stop short of the former, it is evident that these were for the passage of blood-vessels and not receptacles for bristles.
In Propalaeohoplophorus the scutes of the carapace, which are less deeply sculptured than in the larger glyptodonts, are arranged in distinct transverse rows, in three of which they partially overlap near the border of the carapace after the fashion of the armadillos.
The head bears a pair of horn-like scutes, and the scutes of the carapace and tail, which are loosely opposed or slightly overlapping, form a number of transverse rows.
In Arachnida the highest forms exhibit a fusion of the tergites of five post-oral somites to form one continuous carapace united with the terga of the two prosthomeres.
A character of great diagnostic value in the more primitive Arachnida is the tendency of the chitinous investment of the tergal surface of the telson to unite during growth with that of the free somites in front of it, so as to form a pygidial shield or posterior carapace, often comprising as many as fifteen somites (Trilobites, Limulus).
This gives seven somites to the Hexapod's head, the tergites of which are fused to form a cephalic carapace or box.
The small sinuous segmented body is enclosed, except for one small opening, in an enormous sac-like carapace, between the lamellae of which are protruded from the body the ovary and " liver," both large, bifurcate and ramified.
It is this sac-like and not valvular carapace, therefore, that justifies the term Ascothoracida.
CALIPASH and Calipee (possibly connected with carapace, the upper shell of a turtle), the gelatinous substances in the upper and lower shells, respectively, of the turtle, the calipash being of a dull greenish and the calipee of a light yellow colour.
The males are usually more brilliantly coloured than the females, and guard the eggs, which are often placed in a sort of nest made of the shell of some bivalve or of the carapace of a crab, with the convexity turned upwards and FIG.
The most aberrant type of larva is that of the genus Prosopistoma, which was originally described as an entomostracous crustacean on account of the presence of a large carapace overlapping the greater part of the body.
On the surface of the carapace there are in both animals a pair of central eyes with simple lens and a pair of lateral eyetracts, which in Limulus consist of closely-aggregated simple eyes, forming a " compound" eye, whilst in Scorpio they present several AC separate small eyes.
The tergites of this region and those of the following region, the metasoma, are fused to form a second or posterior carapace in Limulus, whilst remaining free in Scorpio.
42) the six somites of the mesosoma are not fused to form a carapace at an early stage, and they are followed by three separately marked metasomatic somites; the other three somites of the metasoma have disappeared in Limulus, but are represented (From Lankester, loc. cit.) by the unsegmented prae-anal region.
Dam, Muscle from carapace to a praeoral entosclerite.
A tendency is exhibited to the formation of a metasomatic as well as a prosomatic carapace by fusion of the tergal surfaces of the somites.
It has been held that the forms with a small number of somites marked in the posterior carapace and numerous free somites between the anterior and posterior carapace, must be considered as anterior to those in which a great number of posterior somites are traceable in the metasomatic carapace, and that those in which the traces of distinct somites in the posterior or metasomatic carapace are most completely absent must be regarded as derived from those in which somites are well marked in the posterior 1 The writer is indebted to R.
On the other hand, it may well be doubted whether the pygidial or posterior carapace is primarily due to a fusion of the tergites of somites which were previously movable and well developed.
In the Phalangiotarbi the appendages resembled those of the Anthracomarti, except that the basal segments of the last four pairs were usually approximated in the middle line leaving a long and narrow sternal area between; and the carapace of the prosoma was unsegmented.
In the outward appearance of the adults there is great want of uniformity, one set having their limbs sheltered by no carapace, another having a broad shield over most of them, and a third having a bivalved shell-cover within which the whole body can be enclosed.
The former, with the feet for the most part concealed by the carapace, is subdivided into two tribes, the Ctenopoda, or " comb-feet," in which the six pairs of similar feet, all branchial and nonprehensile, are furnished with setae arranged like the teeth of a comb, and the Anomopoda, or " variety-feet," in which the front feet differ from the rest by being more or less prehensile, without branchial laminae.
The Gymnomera, with a carapace too small to cover the feet, which are all prehensile, are divided also into two tribes, the Onychopoda, in which the four pairs of feet have a toothed maxillary process at the base, and the Haplopoda, in which there are six pairs of feet, without such a process.
He has applied the theory with especial ingenuity to the interpretation of the circular bony plates in the carapace of the aberrant leather-back sea-turtles (Sphargidae) by prefacing an initial land phase, in which the typical armature of land tortoises was acquired, a first marine or pelagic phase, in which this armature was lost, a third littoral or seashore phase, in which a new polygonal armature was acquired, and a fourth resumed or secondary marine phase, in which this polygonal armature began to degenerate.
Biologie der Algen, by permission of Gustav Fischer.) Dermatophyton grows on the carapace of the tortoise and Trichophilus nucleus, each cell is found to contain many small nuclei, and is in the hairs of the sloth.
The turtle is also found, the carapace being exported as tortoiseshell, the animal being gently roasted or boiled alive over a slow fire to facilitate the separation of the shell from the flesh.
A membranaceous carapace separates the Euco piidae from the more solidly invested Lophogastridae.
Even where a large number of the somites have fused, there is generally a marked change in the character of the appendages after the fifth pair, and since the integumental fold which forms the carapace seems to originate from this point, it is usual to take the fifth somite as the morphological limit of the cephalon throughout the class.
P. 115), has a bilobed carapace, ventrally open; Dendrogaster astericola, Knipovitch (Biologisches Centralblatt, 1891, x.
The wall consists of a basis of cellulose, and in some cases readily breaks up into a definite number of plates, fitting into one another like the plates of the carapace of a tortoise; it is, moreover, often finely sculptured or coarsely ridged and flanged.
The bivalved carapace has a jointed rostrum, and covers only the front part of the body, to which it is only attached quite in front, the valve-like sides being under control of an adductor muscle.