TORTOISES. 9 



Coriaceous Turtle). A very large species of the Mediterranean (a). 

 Its shell is oval and pointed behind, exhibiting three projecting lon- 

 gitudinal ridges *. 



4. The Chelys, or Large-mouthed Tortoises. — CiiELYsf, Dumeril. 



The Chelys resemble fresh-water Tortoises in their feet and nails; 

 their envelope is much too small to contain their head and feet, which are 

 very large, and their nose is lengthened out into a small snout; their 

 most marked character, however, consists in their mouth, which opens 

 crosswise, being unarmed with the liorny beak common to the other Che- 

 Ionia;, and similar to that of certain Batrachians, the Pipa in particular. 

 Test, fimbria, Gm. ; La Matamata, Bruguiere's Journ. d'Hist. 

 Nat. I, xiii; Schapf. xxi. Tlie shell studded with pyramidal eleva- 

 tions, and the body edged all round with a pinked fringe. It is found 

 in Guiana. 



5. The Soft-shelled Tortoises. — Trionyx, Geoff. 



The Soft-shelled Tortoises have no scales, the shell and sternum being 

 simply enveloped by a soft skin ; neither of those shells is completely sup- 

 ported by bones, the ribs not extending to the edges of the sternal one, 

 and united with each other only for a portion of their length, the parts 

 analogous to the sternal ribs being replaced by simple cartilage, and the 

 sternal pieces partially notched as in the sea-tortoises, not covering the 

 whole lower surface. After death, we can see through the dried skin 

 that the surface of the ribs is very rough. Their feet, like those of the 

 fresh-water Tortoises, are palmated without being lengthened, but only 

 three of their toes are possessed of nails. The horn of their beak is in- 

 vested externally with fleshy lips, and their nose is prolonged into a little 

 snout. Their tail is very short, and the anal opening is pierced under its 

 -extremity. They live in fresh water, and the flexible edges of their shell 

 ■aid them in swimming. 



Trionyx ccgyptiacus, Geoff. Ann. du Mus. XIV, 1; Test, tri- 

 vnguis, Forsk and Grael. (The Tyrse, or Soft shelled Tortoise of 

 the Nile), is sometimes three feet in length, and of a green colour 

 spotted with white ; its shell is but slightly convex. It devours the 

 young Crocodiles the moment they leave the egg, and is thus of more 

 utility to Egypt than the Ichneumon;;};. 



Test, ferox, Gm. ; Penn. Phil. Trans. LXI, x, 1 — 3 ; cop. 

 Lacep. I, vii; Schoepf. xix. (The Soft-shelled Tortoise of Ame- 

 rica), inhabits the rivers of Carolina, Georgia, the Floridas, and of 

 Guiana. It remains in ambush under roots of reeds, &c. whence 



* Add, Dermochelis atlantica, Lesueur. 



t Merrem prefers calling this genus by the barbarous name of Matamata. 



X Souuini, Voy. en Egypte, torn. II, p. 333. 



1^" (a) A Lirge specimen of this species, caiiglit on the coast of Devonshire, is to 

 be seen in the i'lritish Museum. — Eno. Ed. 



