EM YD ID AE. 463 



Fam. EMYDIDAE. 



The head is widest across the temporal region ; it tapers towards 

 the rostrum, which is generally truncated. The carapax is quite 

 arched in the direction of both its length and width, it being deepest 

 and broadest upon its middle, and declivous anteriorly and poste- 

 riorly. The plastron or lower surface is very broad and flattened. 

 The point of union between the carapax and plastron is sloping in- 

 wardly downwards, the free edges of both the carapax and plastron 

 projecting considerably beyond the body. 



The limbs are rather stoutly built, though not constructed to sup- 

 port the body. The toes are quite variable, according to the pecu- 

 liarities of habits : long and broadly webbed in such as live mostly in 

 water ; short and scarcely webbed in those that are more frequently 

 found on dry land. 



The carapax is composed of eight vertebral plates, attached to the 

 united vertebrae, of two independent plates, and on each side of eight 

 costal plates. Its periphery consists of twenty-four plates, eleven 

 lateral pairs and two odd ones, one in front, the other behind. The 

 plastron, which is either hinged or immovable, consists of nine plates, 

 four pairs and an odd one; the second and third pairs constituting the 

 points of union to the carapax. 



The exterior surface of both the carapax and plastron exhibits large 

 epidermic scales, the disposition of which varies somewhat according 

 to the genera. 



Most species of this family resort more or less to the waters in 

 marshes and pools, along the edges of ponds or still streams ; the 

 group of Cistudinina alone being exclusively terrestrial. 



The average size of the species varies, within considerable limits, 

 from four to fifteen inches in total length. 



They are harmless and inoffensive, feeding on insects and worms,^ 

 and vegetable substances also : captives, they will eat various kinds of 

 fruits and berries. 



They lay a variable number of eggs, on dry land, in holes, which 

 they dig with their hind limbs. The eggs are elongated and elliptical, 

 the shells of which are not brittle, but rather flexible, and less calca- 

 reous than in the other families. 



