TKSTUIMNID^K. 



*WI 



1 he tibia is a stout hone, whose form may be learned from figure 497, winch represents the 

 left tibia of No. 130 1, just mentioned. It is a much stouter bone than is the corresponding bone 

 in Gopherus polyphemus. Its length is seven-tenths that of the femur, whereas in G. poly- 

 phemus the tibia is eight-tenths the length of the femur. 



The lower end of the fibula is quite as broad as that of the tibia. Professor Cope figured 

 one of the metatarsals (Ext. Batrach., Rept., Aves N. A., plate vii, fig. 10). 



In a collection ot fossils, including some vertebrates purchased bv the American Museum 

 of Natural History from the late ]ames Hall, there are several eggs which are regarded as 

 those ot S. riebrascensis. This identification rests on the facts that these eggs were collected in 

 the White River deposits of Dakota, in which great numbers of this species occur and a few 

 other species of tortoise and that they agree closely in size and form with those of Gopherus 

 polyphemus, as represented bv Agassiz's figure (Contrib. Nat. Hist. U. S., ii, plate vii, figs. 

 28, 29). These eggs appear to have been globular, altho now shorter along one axis, a condition 

 doubtless due to pressure. The diameter along all the axes, except the shorter, is 47 mm.; along 

 the shorter, 43 mm. Fig. 4, plate 59, represents one of these eggs four-fifths the natural size. 



The eggs of G. polyphemus figured by Agassiz have diameters varying from 40 mm. to 

 45 mm., the axes ot the same egg being, in some cases, unequal. 



493. 495. 406. 407. 



Figs. 493-447. Stylemys riebrascensis. 



493. Left ulna, radius, and three carpal bones; palmar surface. Xl. No. 702 



A.M.N.H. int, intermedian; rad, radius; ul, ulna; u/n, ulnare. 



494. Digit, dorsal surface. X 1. No. 701 A. M. N. H. 



495. Pelvis, left side. Xi. No. 1301 A. M. N. H. il, ilium; pub, pubis. 



496. Left femur, tibial border. X?. No. 1301 A. M. N. H. 



497. Left tibia, dorsal surface. X3. No. 1301 A. M. N. H. 



No. 1435 A. M. N. H. is a specimen of a very young turtle of this species which was col- 

 lected by one of the American Museum's expeditions to South Dakota. The shell is nearlv 

 complete, but is somewhat deprest by the weight ot the overlying rocks. The total length 

 was near 75 mm., the breadth, 70 mm. Altho the bones are loosely connected, there are no 

 fontanels. The plastral lip is relatively broad, and in the middle of each lateral half there is a 

 notch. The free borders of the carapace have been slightly notcht and mucronated; at least, 

 some mucros are seen on the hinder peripherals. 



So far as is known to the writer, no specimens of this species have yet been found in the 

 lowermost division of the Oligocene, the Titanotherium beds. They are most abundant in 

 the Oreodon beds, but occur in the Protoceras beds also. The species is extremely abundant 

 in South Dakota and is found also in Nebraska, Colorado, and Wyoming. In the Cope col- 

 lection in the American Museum are specimens that were collected on Old Woman's Creek, 

 Wyoming, by J. C. Isaac, in 1877. Other specimens were obtained in the Oreodon beds of 

 Logan County, Colorado, by one of the expeditions from the American Museum of Natural 

 History in 1898. 



