qS^ 



The Reptiles of the An 



Eocene. [December, 



but forms no true union with it. These are the Dactylosterna} 

 The species are all aquatic, and many of them of marine habitat; 

 they are the least specialized of the order, after the Athecm. In 

 the second tribe or Clidostema, the plastron and carapace are 

 united by a close suture at their edges of contact between the 

 positions of the fore and hind legs ; and the plastron in addition, 

 sends upwards, at the armpit and groin, on the inner side of the 

 carapace, a process or abutment, which gives great strength to 

 the union. In this division belong the fluviatile and many land 



"ormation of Wyoming, 



tortoises. The third division, or Lysoiterna, is less abundantly 

 represented by species than the other two. The plastron and 

 carapace are closely joined, but not by suture. Their straight 

 l See Proc. Amer.' Philos. Society, 1881, p. 143. 



