TESTUDIXATA. Ill 



TESTUDIXATA. 



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

 analysis of the extinct genera of the Cryptodire division, which have been 

 found in North America and Europe up to the present time. 



In the check-list of the North American Batrachia and BeptUia,^ I 

 enumerated 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. Plastrou uot articulated to tlie 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 Cheloniida'. 



Phalanges of anterior limb without condyles ; nine or mtfre costal bones . Propleuridce. ' 



Phalanges of anterior limb with condyles ; digits inclosed in tlistinct integ- 

 uments ; eight costal bones ; sternal elements united by digita- 

 tions and inclosing fontanelles ; caudal vertebrae procoelous . Trionychidce. 



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

 bones ; .•sternal elements united by suture and mclosiug no 

 fontanelles ; caudal vertebrae opisthocoelous Chelydridw. 



II. Plastrou uniting with the costal bones of the carapace by 



suture, with ascending axillary and inguuial buttresses. 

 (Feet, ambulatory.) Clidosterna. 



A Intersternal bones present. 



No intergular scuta Pleurosternidce.\ 



Intergular scuta ; caudal vertebrae optisthocoelous . Baenidce. 



A A 'So intersternal bones. 



a Intergular scuta. 

 A mesosternal bone . . Adocidce. 



a a Xo 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 Testtidinidw. 



III. Plastron uniting with the marginal bones of the carapace 

 by straight suture only. (Feet, ambulatory.) Lysosterna. 



No intersternal bone nor intergular scutum; a mesosternal bone and 



three series of phalanges Cistudinidce. 



The extinct species of the Cryptodira of this continent belong to eight 

 of the above families. I give diagnoses of the genera to which they are 

 referred. Names of existing genera are in Roman type. 



* Bulletin U. S. NatioDal Museum, No. 1, 1875. p. 16. 



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

 •vrith smooth shell, and Helochchjs Meyer, with 8culi)turod shell. 



