43 



FOSSIL TURTLES OF NORTH AMERICA. 



This species differs from T. undata Cope in that the posterior peripherals do not have a 

 strong recurvature outward and the internal thickening is much below the border joining the 

 costal bones. From T. klrttiana, based on a pygal bone, it differs in not having the right and 

 left borders parallel, but diverging upward. The upper border is notcht for the second supra- 

 pygal. From T. orthopygia it differs in having a more elongated skull, a broader plastral lip, 

 and the posterior peripherals less abruptly curved upward near their free border. 



The front of the plastron of the younger specimens of this species bears considerable resem- 

 blance to the same part of T. niobrarensis figured by Dr. Leidy (Cont. Ext. Vert. Fauna West. 

 Terrs., 1873, p. 225, plate iii, fig. 4). It appears however that the lip of Dr. Leidy's specimen 

 projects farther beyond the points where the sulci on each side of the lip cross the border of the 

 plastron, about two-thirds of the lip extending beyond these points. In the specimens of T. 

 osborniana at least half of the lip is behind these points, and usually more of it. Only in the 

 type specimen is there half of the lip in front ot the line joining the points referred to. In 

 Leidy's species, moreover, the front border of the entoplastron falls behind the ledge formed by 

 the lip; whereas, in T. osborniana the front of the entoplastron is slightly in front ot the ledge 

 of the lip. Dr. Leidy's species almost certainly belongs to a different geological level. 



Of this fine species, which has been named in honor of Prof. Henry F. Osborn, of the 

 American Museum of Natural History, there are, in the museum mentioned, specimens which 

 give us a knowledge of the whole osteology and of various stages of growth. 



56.?. 



564. 



565. 



lies. 56^-565. Testudo arenivaga. Pygal and eleventh peripheral of type. Xi 



563. Pygal, eleventh peripheral, and part of suprapygal. 



564. Section of pygal and suprapygal along midline. 



565. Section of eleventh peripheral at union with tenth. 



Testudo arenivaga Hay. 

 Figs. 563-565. 

 Testudo arenivaga, Hay, Ann. Carnegie Mus., iv, 1906 (1907), p. 16, figs. 6-8. 



The present species is based on a fragmentary individual which belongs to the Carnegie 

 Museum, Pittsburg, Pennsylvania. The catalog number is 1509. The remains were found in 

 1905, in beds regarded as belonging to the Lower Miocene formation. The locality is about 

 2 miles north of Agate Springs quarry, in Sioux County, Nebraska. The pygal and the eleventh 

 peripheral are selected for description. 



The pvgal (figs. 563,564) has a height, from the free border to sulcus crossing the hinder- 

 most suprapygal, of 1 12 mm. The width at the upper, or anterior, border is 102 mm.; at the 

 free border, 58 mm. The upper border is deeply notcht for the last suprapygal, the distance 



