Carapace

“ Midway between the eyes is a small flat node or elevation, on each side of which is a larger longitudinal prominence. There are also two similar nodes above the posterior margin. The posterior angles show two oblique short ridges. These elevations of the carapace probably indicate the positions of internal organs and the points of attachment of muscles.
The surface ornaments are not well-preserved, the specimen shows numerous small tubercles, especially over the posterior portion.
The carapace has a length of 8.5 mm. and a breadth of 15 mm. ”

“ Body elongate, slender. Head short and without a carapace. Thorax with eight segments. Abdomen with four segments, the posterior bearing a pair of expanded caudal rami.
Head sub-quadrangular in outline, composed of five coalesced segments, the posterior four of nearly equal width and the anterior narrow. The segmentation of the head is very plainly shown on some specimens (fig. 12) and not on others (fig. 10) . I have inclined at times to consider that there was a cephalic carapace, but finally decided that if present it was very small and thin and not to be recognized as a true carapace. ”

“ In figure 5 the carapace has been pushed forward and turned over so as nearly to reverse its true position. In figure 4 it has been compressed laterally so as to give the posterior parts a wing-like appearance. The test was so delicate that only a few specimens show even approximately the original outlines.
Body long and slender. It is divided into a head, trunk or thorax, abdomen, and tail.
The head cannot be clearly described as it is largely concealed by the carapace. The presence of appendages indicates that 5 segments are combined to form it. ”

“ Shows the split between carapace and marginal shield of underside, through which the animal probably emerged in molting; also the median suture of the marginal shield, and the immature female genital appendage of the operculum. Natural size 2 A half doublure or marginal shield of carapace. ”

“ Carapa, kar′a-pa, n. a genus of tropical trees of natural order Meliaceæ, a South American species yielding the useful carap-oil or crab-oil. [Caraipi, the native Guiana name.]
Carapace, kar′a-pās, n. the shell of the crab, tortoise, &c.—adj. Carapā′cial. [Fr.—Sp. carapacho.]
Carat, kar′at, n. a weight of 4 grains: a proportional measure of 1⁄24 in stating the fineness of gold. [Fr.,—Ar. qīrāt, perh. from Gr. keration, a seed or bean used as a weight.] ”

“ The large, highly arcuate eyes, with disc-like palpebral lobes, are located on the anterior of the carapace, close together, and intramarginally. There is no trace of any ocelli or ocellar mound and enough of the carapace is present to assure their preservation if they were present. The surface is smooth.
At the anterior of the carapace, the ventral shield is faintly preserved as an impression reflected through the carapace. The holotype previously had been carelessly excavated with a sharp instrument toward the anterior, but part of the doublure can still be discerned. ”

“ Description.—Plastral length of adult male, 9.6 centimeters (KU 46911) ; of largest female, 18.4 centimeters (KU 46903) .
Adult male: anterior edge of carapace smooth; septal ridges reduced; pale outer rim, and small, whitish, dots posteriorly on carapace; surface of carapace slightly gritty or sandpapery posteriorly; snout broadened; over-all dorsal coloration dark gray or slate; contrasting pattern on soft parts of body lacking; ventral surface whitish having few blackish marks posteriorly on undersurface of carapace.
Females: posterior margin of carapace usually having fine corrugations ”

“ The carapace is subquadrate in outline, narrowing slightly toward the base. The frontal margin is the most convex, increasing in prominence with advancing age and in the largest specimens becoming distinctly angular. The antelateral angles project but are well rounded; behind them the carapace contracts somewhat rapidly and widens again in the posterior half forming low cheeklike projections of the lateral margins. ”

“ The plastron, without forming a bridge, is connected with the carapace by ligaments, and is divided into two movable lobes, the transverse hinge being so perfect that the box can be completely closed after head, legs, and tail have been withdrawn. The nuchal shield is very small; the first four neurals are large and broad, the fifth much broader than long. There are twelve pairs of marginal shields. The carapace is high and arched. The digits are almost completely free. The tail is very short. The skull is without a bony temporal arch, the quadrato-jugal and the jugal being absent. ”

“ The distal parts of the second through the ninth pair of ribs extend laterally beyond the lateral edges of the pleurals. There are no marginal ossifications. The posterior part of the bony carapace bears blunt, rounded or ovoid to linear, prominences mostly on the last pair of pleurals principally on large females of spinifer and ferox; I have seen only one adult male (stuffed, MCZ 46633) having a semblance of welts on the bony carapace. The nuchal, pleurals and neurals are sculptured. ”

“ Terrestrial Tortoises are distinguished by their short, oval, and convex bodies, covered by carapace and plastron; four feet, and the absence of teeth; short, stumpy, unshapely legs; nearly equal toes, armed with claws, united by a thick skin, so as to form a clumsy foot, the periphery of which forms a sort of hoof, which seems adapted for the land.
In this group the carapace is very convex, its height sometimes exceeding its breadth; it forms a solid, generally an immovable, arch, under which the animal can completely conceal its feet and tail. ”

“ In ordinary Crustacea the carapace, like the rest of the chitinised and calcified integument, is shed off in successive moults, and is restored again as a whole. But in Estheria (and one or two other small crustacea) the moult is incomplete: the old carapace is retained, and the new, growing up underneath it, adheres to it like a lining, and projects beyond its edge: so that in course of time the margins of successive old carapaces appear as “lines of growth” upon the surface of the shell. ”

“ The carapace is very dark brown or black, each shield with a yellow or orange centre; the plastron is brown and yellow, the dark colour being mostly confined to the middle portion. The ground-colour of the skin of the limbs is blackish, but the scales are orange or red. The head is yellow and black. This species inhabits the forests, and lives chiefly on the fruits of trees; in captivity they are said to take bread soaked in milk or water, lemons, apples, bananas, cabbage, gourds, and also meat, at least the males. ”

“ These are symmetrical crabs with a long carapace; the abdomen, which is as broad as the carapace, is always carried flexed under the thorax, and the sixth pair of pleopods are expanded to form with the telson a fan-like tail. The most anterior pereiopods are always much elongated and chelate; while the last pair are much reduced, and either turned up on to the dorsal surface, or else carried in the branchial chamber. ”

“ Cephalothorax. Outline of carapace or cephalothoracic shield semielliptic. In the type of the species, the carapace of a young individual, the lateral margins converge but slightly forward; the anterior angles formed by the projecting eyes and the anterior margin being well rounded. In mature carapaces the lateral and anterior margins are less rounded and more nearly straight, the lateral margins subparallel. ”

“ The plates of the carapace were united by suture in the fossil species, rendering the armor as rigid as the carapaces of land-tortoises. In living forms, the plates, in some species at least, are slightly separated by intervening integument, rendering the armor more or less flexible throughout. ”

“ Associated with the development of the carapace, in this and in the next family, is a remarkable condition of the lateral eyes, which are sessile on the dorsal surface of the head, and near the middle line, the median eye being slightly in front of them. During embryonic life a fold of skin grows over all three eyes, so that a chamber is formed over them, which communicates with the exterior by a small pore in front. ”

“ Every one who has eaten a boiled crayfish, or a lobster, knows that the great shield, or carapace, is very easily separated from the thorax and abdomen, the head and the limbs which belong to that region coming away with the carapace. ”

“ The carapace, as in the Conchostraca, forms a bivalved shell, but does not enclose the head. There is a single large eye, which really corresponds to two eyes fused together. A pair of large antennæ, each with two branches, carrying long feathered hairs, project at the sides of the head, and are used in swimming with a peculiar jumping motion, from which the popular name of the animals is derived. There are not more than six pairs of feet. ”

“ When the legs are disengaged, the animal draws its head and limbs completely out of their former covering; and, with a sudden spring forward, while it extends its abdomen, it extracts the latter, and leaves its old skeleton behind. The carapace falls back into its ordinary position, and the longitudinal fissures of the sheaths of the limbs close up so accurately, that the shed integument has just the appearance the animal had when the exuviation commenced. ”

“ The form of the carapace is clearly that of S. myops which is the only one in the Otisville fauna possessing a subrectangular outline; the position of the eyes corresponds to that found in the adult stages of S. myops; the broad rim of the carapace, a characteristic feature of S. myops and not observed in other members of this fauna, is present in these young individuals. ”

“ The illustrations accompanying the description by Salter show the general form of the carapace and abdomen. These taken in connection with seven specimens of the carapace, two of which have several segments of the abdomen attached to them (in the collection of the United States National Museum) , enable me to identify the genus and add materially to the description of Salter. ”

“ Whilst the hinder part of the carapace rises and the above-mentioned fissure is formed, the anterior part seems to sink, and to narrow or entirely close the anterior entrant orifice. Under water the elevation of the carapace never takes place. The animal therefore opens its branchial cavity in front or behind, according as it has to breathe water or air. ”

“ When it wishes to burrow these two limbs are sometimes alternately and sometimes simultaneously thrust backwards below the carapace quite beyond the hinder edge of the shell, and in the act of thrusting the lobes or plates on each leg encounter the sand, the resistance or pressure of which causes them to open and fill with sand, a load of which at every thrusting operation is pushed away from under the crab and deposited outside the carapace. ”

“ In countries where they are common, and where they attain an enormous size, their flesh is the most healthy and nourishing food, and their carapace serves as a canoe in which the natives paddle along the shores. ”

“ The species characters are then the following:
Description. Body medium-sized to large. Carapace semicircular, nearly twice as wide at base as long (length : width as 6 : 11) , probably originally quite high (as indicated by concentric wrinkles) ; lateral and frontal margins forming a continuous circular curve, when the carapace is flattened; the thickened edge scalloped; posterior margin straight and transverse, genal angles nearly rectangular ”

“ The moment this happens, and before the creature has lost its balance on the spine, the false feet make another flap and give another impulse upwards and forwards; all this time the position of the carapace is slanting, the top inclining downwards at an angle of about 45°, the hinder shell being at another angle, and the tail spine hanging down vertically, and so it progresses by a combination of flapping and hopping till it reaches the limits of its tank and sinks to the ground. ”

“ The carapace is marked by wrinkles, which, while in some specimens they suggest nothing, in others, especially old males, bear the strongest and most ludicrous resemblance to the face of an ancient man. ”