CHELONIA. 19 



Trionyx* the Soft-shelled Tortoises. 



These also, like the last, are destitute of plates, 

 the shell and sternum being merely encased by a 

 thick skin, which is widened into a free and flexible 

 margin, and serves, like the side fins of the Flatfishes, 

 to enable them to scuttle along at the bottom of 

 the rivers they inhabit. Their feet have three nails. 

 An American species (T. Ferox) is vigorous and 

 daring, defending itself with great fierceness and 

 activity, darting on its assailant, and biting with 

 great violence. It feeds on birds and other animals, 

 devours young Alligators, and is in turn devoured 

 by the old ones. 



Connecting the Tortoises with the next Order, or 

 rather forming an intermediate one, were some gi- 

 gantic animals which wallowed in the seas of a 

 former condition of our world, " making the deep to 

 be hoary," but of which the fossil bones alone now 

 remain. We will just glance at their strange and sin- 

 gular forms. The first has been named Icthyo- 

 saurus^ literally Fish-lizard ; it combined the snout 

 of a Dolphin with the teeth of a Crocodile ; the head 

 of a Lizard with the spine of a Fish ; the breast- 

 bone of an Ornithorhynchus (Duckbill) with the 



* T}$, treis, three, and oW|, onyx, a nail. 



i ichthys, a fish, and <rat/aj, sauros, a lizard. 



