1881.] 14:3 [Cope. 



i 



REPTILIA. 



Crocodilus sp. Allied to the C. chamensis and G. heterodon, but not 

 represented by sufficiently well preserved specimens to permit of determi- 

 nation. There are numerous molariform teeth in the posterior parts of 

 jaws, and the crowns of the longer teeth are grooved. Not uncommon. 



Emys sp. Rare ; one specimen of 220 mm. in length, of the type of 

 E. wyomingensis, but not sufficiently well preserved for determination. 



As the Eocene forms of this order are of unusual interest, I give an 

 analysis of the extinct genera of the Cryptodire division of tortoises which 

 have been found in North America up to the present time. 



In the check -list of the North American Batraclria and Reptilia,* I enu- 

 merated nine families of this division of the Testudinata, three of- which 

 are extinct. Subsequently another extinct family, the Baenidse, was 

 added. I now define all of these families. 



I. Plastron not articulated to the carapace, but presenting to it more or 

 less open digitations. Dactylosterna. 



Phalanges of anterior limb without condyles, and covered by a common 

 integument ; eight pairs of costal bones Cheloniidce. 



Phalanges of anterior limb without condyles ; nine or more costal bones, 



Propleuridce. 



Phalanges of anterior limb with condyles ; digits inclosed in distinct in- 

 teguments ; eight costal bones ; sternal elements united by digitations 

 and inclosing fontanelles ; caudal vertebrae procoelous. . . TrionycMdce. 



Phalanges of anterior limbs with condyles ; digits distinct ; eight costal 

 bones ; sternal elements united by suture and inclosing no fontanelles ; 

 caudal vertebrae opisthocoelous Chelydridoe. 



II. Plastron uniting with the costal bones of the carapace, by denticu- 

 late suture, and by ascending axillary and inguinal buttresses. (Feet 

 ambulatory. ) Olidosterna. 



A. Intersternal bones present. 



No intergular scuta , Pleurostemidce.^ 



Intergular scuta ; caudal vertebrae opisthocoelous Baenidce. 



A A. No intersternal bones. 



a. Intergular scuta. 

 A mesosternal bone Adocidm. 



aa. No intergular scuta. 



A mesosternal bone ; three series of phalanges Emydidce. 



No mesosternal bone ; three series of phalanges Cinosternidce. 



A mesosternal bone ; two series of phalanges Testudinidm. 



* Bulletin TJ. S. National Museum, No. 1, 1875. p. 16. 



t There are two genera of this family, neither of them yet found in America ; 

 Pleurostemum Off., with smooth shell, and Helochelys Myer, with sculptui'ed 

 shell. 



