28 REPTILE GALLERY. 



[Cases 4. The Emydidce, or Freshwater Tortoises, possess a perfectly 



'■' ossified carapace covered with epidermoid plates, and movable 

 digits furnished with 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, Case 33), in which the tail attains to a great length, 

 and is furnished with a crest resembling that of a Crocodile ; Che- 

 lydra temminckii is the largest freshwater 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 (Emys picta, rivulata, ornata, &c, Case 36). The Euro- 

 pean species (Lutremys europaa, 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. Pyxidea, Geoemyda, Lutremys live as much on land as 

 in water; and, finally, we have an example of an exclusively ter- 

 restrial Emydoid in the Box-Tortoise (Cistudo Carolina, Case 38), 

 which lives in the woods of the southern parts of the United States, 

 and possesses, like other Freshwater Tortoises, a hinge in the 

 lower shield, rendering its anterior portion movable. A lid is thus 

 formed by which the posterior opening of the shell can be com- 

 pletely 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 Podocnemys expansa (Case 

 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 (Chelys fimbriata, 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. 

 ,- p 5. Testudinidce, or Land Tortoises, with verv convex carapace, 



39_44.] and with feet adapted for progression on land only. They are 



