762 THE WHITE EIVER FAUNA. 



The species are none of them of remarkable size, but coincide with 

 the average of the species now found in the same region of the continent. 



TESTUDINATA. 



The species of this order which have been found in the Miocene beds 

 were of terrestrial habits. They belong to two genera, Testudo and Sty- 

 lemys. That the lakes of this period were haunted by aquatic tortoises was 

 to have been anticipated, but as yet they have not been found. 



TESTUDO Linn. 



As no jaws of the Miocene species have yet been found, it is not cer- 

 tain whether they, belong to the genus above named, or to Xerobates Agass., 

 with the Loup Fork species. 



Five species which I refer here, left their remains in the White River 

 beds of Colorado. As but one species had been previously identified from 

 the White River formation, the discovery of these was unexpected. The 

 numerous individuals found by Dr. Hayden in the Mauvaises Terres of 

 Dakota and Nebraska were all referred by Dr. Leidy to the Stylemys nebras- 

 censis. The same species is found in Colorado, but associated with the five 

 species here described. 



The difi'erences between these Testudos are well marked, and are best 

 appreciated by reference to the plastron, though not wanting in the cara- 

 pace also. The principal characters are the following : 



I. Each half of the lip of the plastron trihedral, as deep as wide. 



Marginal bones short and thick, with simple dermal grooves T. cultratus. 



II. Halves of the lip of the plastron flat, thinner than wide. 

 a. Gular scuta square. • 



Lip prominent, with straight sides T. quadrattis. 



aa. Gular scuta triangular. 

 \a\> prominent, narrowed forwards, border with several teeth ; posterior lobe dentate; 



marginals wide, mucronate T. laticuneus. 



Lip prominent, with parallel sides and entire margin ; marginals wide, with notched 



border T. ligonius. 



Lip not prominent, truncate, entire; marginals wide, notched medially. . T. amphithorax. 



None of the varieties of the Stylemys nehrascensis present the well-defined 

 lip of the plastron seen in these species, nor do its marginal bones ever have 



