170 PROCEEDIiSrGS OF THE NATIONAL MUSEUM vol. S3 



1919 I added the species B. aWertensis. Both of the type specimens 

 were from the Belly River formation, Upper Cretaceous of Alberta, 

 Canada. A specimen about to be described records the first occur- 

 rence of this genus outside of Canada. 



Hay (1908) characterized the genus as follows: 



Like Baena, but having on each side supramarginal scutes, which alternate 

 with the costal scutes. Nuchal bone short and wide. A preneural present. 



I would amend this definition by the addition of the following 

 characters : Five or six vertebrals, last vertebral separated from pos- 

 terior border by supracauclal scutes. This is a character found 

 among the Baenidae only in Boremys and Thescelus. 



Boremnjs indchra: Small size, front of shell broadly rounded; 

 costal scutes wider than long. Five vertebral scutes. 



Boremys oZbertensis: Small size, front of shell bluntly pointed; 

 costal scutes longer than wide. Five vertebral scutes. Anterior lobe 

 of plastron shorter than posterior lobe. 



Boremys grandis: Large size, front of shell broadly rounded; 

 costal scutes longer than wide. Six vertebral scutes. Anterior lobe 

 of plastron longer than posterior lobe. 



BOREMYS GRANDIS, new species 



Figures 9, 10: Plate 35 



Type. — U.S.N.M. no. 12979, consisting of a nearly complete cara- 

 pace and plastron. Collected by George F. Sternberg, 1929. 



Type locality.— ^'SNY^, T. 24 N., R. 13 W., 3 miles northeast of 

 Hunter's Store (Bisti P. O.), San Juan County, N. Mex. 



Horizon. — Kirtland formation, Upper Cretaceous. 



DesoHption. — The specimen selected as the type lacks iiortions of 

 the lateral borders and is somewhat depressed by vertical crushing. 

 The shell is subquadi'angular in outline, being longer than wide, 

 with a broadly rounded anterior end and a truncated posterior bor- 

 der. Its large size at once distinguishes it from known species, 

 as it is more than twice the size of B. pulchrci and fully twice as 

 large as B. aZbertensis. In this specimen the plastron projects 

 strongly in front of the anterior border of the carapace, as in 

 Thescelus; this feature, however, may be in part due to the crushing 

 to which the specimen has been subjected. 



The surface of the shell is undulating and is devoid of ornamenta- 

 tion, except for low-lying bosses that are sparsely scattered over 

 the supramarginal and marginal areas. The central part of the 

 Ciuapacc is fairly smooth, with slight indication of a median keel 

 fore and aft. 



