91 



COMPSEMYS, Leidy. 



This genus presents the characters of Emys in its well-developed 

 marginal bones, united to the costals by suture. The surfaces of the 

 carapace possess a dense layer, which is sculptured in two of the known 

 species. One of these, the G. rictus, Leidy, has been found to have had a 

 wide range in the West during the Fort Union epoch; while a second has 

 been found in corresponding strata near the northern boundary of Dakota. 



COMPSEMYS OGMIUS, Cope. 



Represented in the collections of the British American Boundary Com- 

 mission by portions of the carapace and plastron. These are massive, and indi- 

 cate a species of large size. As in other species of the genus, the external 

 surface is a dense layer of cement or allied substance, which is sculptured 

 with shallow pits. 



A portion of the costal bone is concave, and increases rapidly in thickness 

 in one direction. The suture is coarse, but neither gomphosial nor squamosal. 

 A portion of the plastron is thinner, not curved, and displays a very coarse 

 median suture, in part squamosal in character. The sculpture consists of shallow 

 pits, not wider than the low, smooth ridges which separate them. There are 

 deep superficial grooves, marking the boundaries of dermal areas; a feature in 

 which this tortoise differs much from the P. coalescens, and resembles the 

 species of Compsemys. Should marginal bones be found to exist in the P. 

 ogmius, its reference to that genus will be further established. 



From six miles west of first branch of Milk River, near latitude 49°. 



ADOCUS, Cope. 



Proceedings of the Academy of Natural Sciences, Philadelphia, 1868, p. 235; Proceedings of the 

 American Philosophical Society, 1870, November. 



This genus possesses a large intergular plate. This I have verified on A. 

 beatus and A. syntheticus. Having also perfect xiphisternal bones of these two 

 species, I can show that there is no sutural attachment for the pelvic bones. 

 The co-existence of these two characters has been hitherto found to be uni- 

 versal, and the present deviation from it is a point of much interest. Instead 

 of sutural surfaces, there is an obtuse ridge corresponding to the pubis, and a 

 knob answering to the extremity of the ischium, both more prominent than is 

 usual in genera of Emydidos. 



