:2S REPTILE UAl.IJ.ltY. 



' 4. The Emydida, or Freshwater Tortoises, possess a perfectly 



ossified carapace covered with epidermoid plates, and movable 

 digits furnished ^itli sharp claws. The mode of life of some is 

 aquatic, of others almost terrestrial; the former having their shell 

 least convex, and a more or less developed web between the toes. 

 Thoroughly aquatic are the Alligator Terrapens of North America 

 [Chelydra and Macroclemmys, Case 33), in which the tail attains 

 to a great length, and is furnished with a crest resembling that 

 of a Crocodile ; Macroclemmys temminckii is the largest fresh- 

 water Tortoise. The East-Indian Batagur (Case 34) approach in 

 their physiognomy and habits and in size the Freshwater Turtles. 

 The smaller forms are most abundant in North America, and 

 sometimes beautifully marked (Clemmys picta, rwulata, ornata, &c., 

 Case 3G). The European species (Emi/s orbicularis, Case 38) is 

 abundant in South Europe, and found, less frequently and locally, 

 in Germany as far north as Berlin ; its fossil remains have been 

 found in the fen-country. Nicoria, Geoemyda, Cyclemys live as 

 much on land as in water; and, finally, we have an example of an 

 exclusively terrestrial Emydoid in the Box-Tortoise (Cislmlo 

 Carolina, Case 38), which lives in the woods of the eastern and 

 southern parts of the United States, and possesses, like Emys, hinges 

 in the lower shield, rendering its anterior and posterior portions 

 movable. A lid is thus formed by which the openings of the shell 

 can be completely closed. 



The following Freshwater Tortoises differ from the preceding in 

 not being able to retract the head and neck, but in bending it side- 

 ways under the shell, as the American Podocncmi/s e.rpnnsa (< 

 31), of which a fine skeleton is exhibited, and the Australian 

 Chelodina. But the most remarkable form of this group is the 

 Mata-Mata Tortoise {Chclys fimbriate! , Case 31), a native of Brazil 

 and the Guianas. Its head and neck are fringed with warty appen- 

 dages, floating in the water like some vegetable growth, whilst the 

 rough, bossed carapace resembles a stone, — an appearance which 

 evidently is of as great use to this creature in escaping the obser- 

 vation of its enemies as in alluring to it unsuspicious animals on 

 which it feeds. 



5. Testudinidts, or Land Tortoises, with very convex carapace, 



CtW ' -iii mi 



30-44.] and with feet adapted for progression on land only. 1 hey are 



