SOFT-SHELLED TORTOISES. 35 



in Greece and Italy. Its flesh is used as food, and it is reared 

 for that purpose, with bread, young vegetables, &c. 



23. Some fresh water Tortoises have the sternal plastrum 

 divided into two flaps, which they can at will, by a moveable 

 articulation, close against the carapax, when their head and ex- 

 tremities are drawn in, so as to inclose themselves in a box ; this 

 peculiarity has obtained for them the name of Box-tortoises. 



24. There are some fresh water Tortoises, on the contrary, 

 that cannot enclose themselves within the shell. Amongst these 

 is the Snapper, Testudo serpentina, which is readily distin- 

 guished by its long tail, which is studded with sharp crests. It 

 is found in the warm parts of the United States. 



25. The FAMILY OF RIVER TORTOISES, (or Soft-Shelled Tor- 

 toises,) Trionyx, differ from all the preceding in the conforma- 

 tion of their paws, which are designed for swimming, but are 

 entirely unsuited for walking. The paws are very*much depressed, 

 and the toes, although very distinct, and more or less moveable, 

 are joined as far as the nails by broad flexible membranes. The 

 carapax is very much spread out, and almost flat, unprovided with 

 scales, covered only by a skin which is soft, and entirely cartila- 

 ginous throughout its border, which structure has obtained for 

 them the name of Soft-skelled 7 J ortoises; the neck is generally 

 elongated and protractile ; the nostrils are prolonged into a sort 

 of little trunk ; the jaws are trenchant, and furnished with a fold 

 of skin, which resembles lips ; the limbs are short, and supplied 

 with only three toes. To these external characters are added 

 other anatomical peculiarities ; for example, the carapax has no 

 marginal pieces, and the sternal plastrum is not ossified in the 

 middle. 



26. These animals are essentially aquatic, and inhabit the 

 rivers and lakes of the warmest regions of the globe : they swirn 

 with great ease, and remain on land only at night ; they are very 

 voracious, and feed chiefly on reptiles and rishes. 



27. The Nile supports one species of these Tortoises, which 

 is useful to Egypt by devouring a great number of young croco- 

 diles the moment they are hatched; it is the Tyrse, Trionyx 

 cegyptiactis, of Zoologists. Another species, which inhabits the 

 rivers of South America, is remarkable for its ferocity, and for 

 the delicacy of its flesh. 



23. What are Box -Tortoises ? 



24. What is the Snapper ? 



25. What are the characters of the Sofl-Shelled Tortoises ? 



26. What are their habits? 



27. What is the Tyrse ? 



