322 



SYSTEMATIC ZOOLOGY 





with its long neck, the four legs, and the tail can generally be 

 drawn under the edge of the carapace so as to be scarcely 

 visible ; they are covered with a scaly epidermis, resembling 

 that in the Squamata. 



The appendages may have the digits distinct and terminating 

 in bony claws, or they may have membranes between them, or 

 they may all be inclosed in the integument so that the appendage 

 becomes a paddle-like structure or flipper instead of a foot. On 

 the head are the tympanic membranes; the eyes are provided 

 with eyelids; the jaws are entirely without teeth, but have very 

 sharp cutting edges consisting of the hard, horny epidermis ; 



b'lG. 325. Testudo graeca, Greek tortoise. (Alter Brehm, from Parker and Haswell's 



Manual.) 



the tongue is attached to the floor of the mouth, and is not pro- 

 trusible. The cloaca! opening is at the root of the tail and is 

 circular or longitudinal, not transverse, as in the preceding orders. 

 There is a large urinary bladder on the ventral side of the 

 cloaca, and in the male the copulatory organ consists of a 

 median penis attached to the ventral cloacal wall ; a correspond- 

 ing organ, less developed and known as the clitoris, occurs in the 

 female in a similar position. The turtles are all oviparous, 

 depositing their eggs, inclosed in leathery or calcareous shells, 

 in the sand or earth, where they are left to incubate. 



Some Chelonia feed entirely on plants, others on animals such 

 as fish and various invertebrates. They are essentially tropical, 



