462 



FOSSIL TURTLES OF NORTH AMERICA. 



costo-marginal sulcus. Where thickest, at the line where on the inner surface the horny scute 

 met the soft skin, the bone is 45 mm.; elsewhere from 22 mm. to 30 mm. Considering the 

 great thickness of the neurals and costals we might expect the peripherals of T. crassiscutata 

 to be thicker than is the bone here described. 



Testudo laticaudata Cooe. 

 Figs. 623, 624.. 



Testudo laticaudata, Cope, Geol. Surv. Texas, iv, 1903, reprint p. 75, plate xxii, fig. I. Hay, Bibliog. 

 and Cat. Foss. Vert. N. A., 1902, p. 451. 



The type of Cope's T. laticaudata consists of a nearly entire right epiplastron, said by 

 Cope to be the left, and the greater part of the right xiphiplastron. These remains were found 

 by Prof. W. F. Cummins, of the Texas Geological Survey, in the Equus beds, on Rock Creek, 

 opening into Tule Canyon, in Briscoe County, Texas. These bones are now in the Univer- 

 sity of Texas, where the writer has been permitted to examine them. 



The form of the anterior lobe of the plastron, as far backward as the hyoepiplastral 

 suture, can be seen from Cope's figure here reproduced. The width ot the lobe at the suture 

 mentioned was very close to 205 mm. The epiplastral lip was very slightly set off from the 

 remainder of the lobe and was rounded and slightly tootht in front. The lower surface of the 

 bone is in general flat, but on the lip there are two broad shallow fossae. The free border is 

 acute posteriorly, less so in front of the gulo-humeral sulcus. Along the epiplastral symphysis 

 the bone thickens rapidly (fig. 624) rising to a height of about 42 mm. It then descends 



624. 



623. 



FlGS. 623 AND 624. Testudo laticaudata. 



623. Ri K ht epiplastral and xiphiplastral bones forming type. Xj. a, right epiplastron, lower surface; 



h, upper surface of same bone; r, lower surface of right xiphiplastron; d, upper surface of same bone. 



624. Section along symphysis of epiplastral bones. X5. 



perpendicularly until a thickness of about 20 mm. is attained. At the hyoepiplastral suture 

 the thickness of the bone has become reduced to 19 mm. Along the suture mentioned the 

 thickness is at first reduced slowly, then rapidly to the acute free border. The width of the 

 bone along this suture is 54 mm. The entoplastron had a width of about 100 mm. Its length 

 can not be determined. 



On the lower side of the bone is seen a portion of the gulo-humeral sulcus. It crost the 

 entoplastron, then ran outward and forward, then outward and slightly backward to the free 

 border of the bone. 



Figure 623 c, d, reproduces Cope's figures of the right xiphiplastron, the part on the right 

 representing the upper side of the bone, that on the left the lower side. At the hypoxiphi- 

 plastral suture the free border is rather obtuse. From the border the bone thickens rapidly to 

 a thickness of 25 mm. Further backward the free border becomes acute and the maximum 

 thickness slightly less. At the midline behind it is 23 mm. The hinder angle of the bone is 

 curved slightly upward. The horn-covered surface on the upper face of the bone reaches the 

 free border at a distance of 15 mm. from the midline. The posterior notch was about 120 mm. 



