CHELOMA. 



271 



The Terrapins, or Box-Tortoises, (Terrapene, Merrem ; Kinosternon, Spix ; CLsluda, Fleming), — 

 The breast-plate of which is divided into two pieces by a moveable articulation, and which have the 

 power of completely closing their carapace when the head and limbs are withdrawn into it. 



Some have only the anterior segment of the breast-plate moveable, as T. subnigra, Lin., ami T. c/uusa, Scharff. ; 

 while in others both segments are equally mobile, as T. tricarinata, Sclweff., and T. pennsylvanica, Id. 



There are some Fresh-water Tortoises, 



The Chelydrons {Chelydra, Fitzinger ; Chelonura, Fleming;, — 

 Which have a long tail and great limbs, that cannot be quite withdrawn within their armour. They 

 approximate to some of the following genera, and more particularly to the Chelydes, and should rank 

 as a particular subdivision. 



Such is the Long-tailed Tortoise (T. serpentina, Lin.», which is known by having its tail almost as long as the 

 carapace, and beset with dentelatcd and pointed crests, and pyramidal scales. It inhabits the warm regions of 

 North America, is very destructive to fish and water-fowl, ascends far up the rivers, and sometimes attains a 

 weight of twenty pounds. 



The Turtles {Chelonia, Brongniart; Carelta, Merrem) — 

 Have their envelope too small to receive the head, and more especially the feet, which latter are 

 extremely elongated, (particularly those in front,) flattened to serve as oars, and have all their toes 

 closely united, and enveloped in the same membrane. The two first toes alone of each foot 

 are furnished with pointed nails, and even these are apt to fall, one or the other of them, at a certain 

 age. The pieces which compose their plastron do not form a continuous plate, but are variously 

 dentelated, and leave great intervals, which are occupied only by cartilage. Their ribs are narrowed, 

 and separate one from another at their external portion, but the entire circumference of the cara- 

 pace is occupied by a circle of pieces corresponding to sternal ribs. The temporal fossa is covered 

 over by an arch formed of the parietals and other bones, in such a manner that the whole head is 

 guarded by a continuous bony casque. The oesophagus is internally armed throughout with carti- 

 laginous points, and sharp tubercles directed towards the stomach. 



The Edible or Green Turtle (T. midat, Lin.) is distinguished by its greenish scales, to the number of thirty, 

 which do not cover each other in the manner of tiles, and the medial of which are ranged in almost regular hexa- 

 gons. It attains a length of six or seven feet, and a weight of seven or eight hundred pounds. Its flesh supplies 

 an agreeable viand, very wholesome to mariners traversing the torrid zone. It feeds in great troops upon the 

 algae in the depths of the ocean, and approaches the mouths of rivers to respire. Its eggs, which are deposited in 

 the sand where the sun may warm them, are very numerous, and fine eating; but its shell is not employed in 

 manufactures. 



A neighbouring species (Ch. maculosa, Nobis,) has the middle plates twice as long as wide, and of a fulvous 

 colour, marked with great black spots; and another (Ch. tachrymata, Nobis,) has plates as in the preceding one, 

 but raised into a boss posteriorly, and black splashes upon the fulvous. The scales of both these are useful iu 

 manufactures. 



The Imbricated Turtle (T. imbricata), which is less than the green one, with a more lengthened muzzle and 

 dentelated jaws, and bearing thirteen yellowish and brown scales, which cover each other in the manner of tiles, 

 furnishes the best tortoise-shell employed in the arts ; but its flesh is disagreeable and unwholesome, though the 

 eggs are very delicate. It inhabits the seas of hot climates. 



There are yet two species allied to the Imbricated Turtle, the Ch. virgata, Nobis, the scales of which are more 

 raised, and the medial equal, but with more pointed lateral angles, and radiating black lines ; and Ch. radiata, 

 Scha'ff., which merely differs from the last by having the hindmost of its middle scales wider, being perhaps a 

 mere variety. 



Finally, the Hawk-billed Turtle (T. carelta, Gin.) Is more or less brown or rufous, with fifteen scales, the medial 

 o' Which have raised crests, more particularly towards the extremity; the point of the upper mandible is crooked, 

 and the fore-feet longer and narrower than in the others, preserving also better-marked nails. It inhabits 

 several seas, and even the Mediterranean, subsists on Testacea, has bud flesh, and shell which is tn low estima- 

 tion, but it furnishes an oil that burns well. 



Merrem has recently distinguished, as 



The Lcathkrbacks (Sphargit, 111.; Coriudo, Fleming; Dcrmochclis, I.csueur), — 

 Those species which have no scales, but the carapace of which is invested with a son of leather. 



3UI-I: is a large species of the Mediterranean [which has occurred two or three times on the British somes! 

 (T. cor acia, Lin.), the carapace of which is oval, and pointed behind, with three prominent longitudinal i ui- -■ 



There is another in the Atlantic (Uermochelit atlantica, Lefevrel. 



The Chelydes {Chelys, Dumcril ; Matamata, Merrem) — 

 Resemble the Bmydei by their feet and nails; but their envelope is much too small to in 



