384 



FOSSIL TURTLES OF NORTH AMERICA. 



was obtained by Professor Cope in the neighborhood of Cottonwood Creek, Wyoming, and 

 comes from the Bridger Eocene beds, the level being that known as B. 



Cope's description of this species is very brief and unsatisfactory, not even doing justice 

 to the fragmentary materials at his command; yet including statements that imply that he 

 had more materials than are now accessible. He states that the plastron was concave, yet we 

 have no evidence that other parts of it were present than the half of the anterior lobe. The 

 surface of the carapace is said to be without irregularities of surface, yet no neurals or costals 

 seem to have been secured. 



The size of the individual must have been greater than estimated by Cope. He says that 

 the length was 18 inches, equal to 437 mm. Cope's fig. 14 of his plate represents the ninth, 

 tenth, and eleventh peripherals of the right side, and about half of the pygal. The length of 

 the ninth and tenth taken together amounts to 156 mm. The length of the same two elements 

 of a specimen of H. corsoni whose carapace has a length of 590 mm. is 131 mm. An estimate 

 based on these dimensions makes it probable that the type of the species had a length of about 

 626 mm., or about 25 inches. 



It is improbable that this species belongs to the genus Hadrianus. Two reasons may be 

 assigned for this opinion. The first is found in the fact that there is no epiplastral lip, a 



482. 



483- 



485. 



Figs. 482-485. Achilemys allabiatus. X 3- Type. 



482. Portion of rear of carapace, per. 1 1, eleventh peripheral; py, pygal; spy, suprapygal. 



483. Portion of anterior lobe of plastron, hyo, hyoplastron; enl, cntoplastron; epi, epiplastron. 



484. Section of ninth peripheral. 



485. Section at anterior end of eleventh peripheral. 



structure found in the other species of the genus, except possibly in H. tumidus, the only known 

 specimen of which does not present that region. In Achilemys allabiata this lip is not differ- 

 entiated even so much as it is in the Emydidae. 



The second reason is found in the structure of the hinder region of the carapace. With 

 the other bones of this species at Washington there is a portion of a suprapygal which joins 

 accurately the eleventh peripheral and the pygal of the type. This is represented in its proper 

 position in fig. 482. This bone has the position of the third suprapygal ot Tcstudo and ot 

 Hadrianus corsoni. In the genera just named the sulcus between the last vertebral scute and 

 the supracaudal scute follows closely the suture between the third suprapygal and the pygal. 

 In the species being here described the sulcus crosses the suprapygal at some distance above 

 the suture referred to. It is to be noted also that the three peripherals of this region are 

 travel st by perpendicular sulci from top to free border, showing that the sulcus between the 

 marginal scutes and the costal scutes ran on or above the sutures between the peripheral and 

 costal bones. The position of the sulci of this region in our species resembles somewhat that 

 of Kachuga, as represented by Mr. Boulenger (Cat. Chelonians, p. 53, fig. 16). 



The epiplastron (fig. 483) figured by Cope has the anterior end thickened and rounded 

 in section. More posteriorly this epiplastron has an acute border. At their symphysis the epi- 

 plastra have a thickness of 23 mm. The truncated end of the anterior lobe, the rudimentary 

 lip, has a width of about 125 mm. The scute-covered area on the upper surface is 18 mm. 

 wide. The bone on this surface does not thin backward as in Testudo and Hadrianus. The 

 entoplastron had a width of about 170 mm. It was truncate or cordate behind, notwith- 



