1 882.] The Reptiles of the American Eocene. 989 



applied edges are separated by a thin layer of cartilage only, and 

 there are no buttresses to strengthen the union. These are the 

 tortoises which close the shell partially or wholly, by a hinge across 

 the middle of the plastron ; and they are exclusively inhabitants 

 of the land. 



The families of the Dactylostema are the marine turtles {Chel- 

 oniidce), the snappers, {Chelydridce), a family which connects the 

 two, (Propleuridcz), and the Trionychidce or soft-shelled turtles. 

 The Propleuridce belong to the cretaceous beds only, but the 

 others abound in the Tertiaries. 



In the marine Eocene of New Jersey, parts of huge turtles are 

 found, but enough is not yet known of them to assure us to 



Fig. T.—Anostira ornata Leidy, from the Bridger beds of Wyoming, one-halt 

 Leidy. 



what family they belong, except that they are not Trionychida. 

 The sutures of their shells are very deeply interlocking and splin- 

 tery. They form the genus Lembonax Cope. 



In the lacustrine Tertiaries of the West the only families of Dac- 

 tylostema represented are the Trionycliida and Chelydrtdai. Al- 

 though found in the Western rivers at the present time, the Tri- 

 onychidce are only represented in a fossil state in the Eocene beds. 

 They are unknown in the Miocene of the West, ttiougn com- 

 mon in the marine Miocenes of the coast. Species ot Irionyx 

 are very abundant in the Wasatch and Bridger beds, one ot wnicn 

 is represented in the wood cut, Fig. 6. One genus ot LnelyaruUB 



