NO. 2292. Y;^^;- FOSSIL TURTLES— GILMORE. 129 



The humerals meet on the midline for a distance of 19 millimeters; 

 abdominals for 32 millimeters; femorals for 24 millimeters; and anals 

 for 13 millimeters. 



Echmatemys megaulax, as known at this time, in many respects 

 closely resenbles both E. testudinea and E. euthneta. From the 

 former it appears to be distinguished by the thimiess of the shell and 

 the much narrower beveled surface on the superior lateral borders of 

 the hinder lobe immediately posterior to the inguinal buttresses. 



In the type of E. testudinea the bevelled surface on the mesiad side 

 drops abruptly downward to the level of the plastral surface, whereas 

 in E. megaulax it is not only much narrower (as shown by specimen 

 No. 7316, U.S.N.M.), but lies entirely below the level of the median 

 plastral surface, from which it is separated by a very shallow groove. 

 The specimen before me now shows that the swollen costals, outside 

 of the costovertebral sulci, thought by Hay to be distinctive of E. 

 testudinea, is a feature common to both species. 



Wliile the specimen here considered is like E. euthenta in having a 

 thin shell and a narrow beveled surface on the lateral borders of the 

 plastron, it differs in having all neurals except the first wider than 

 long and a greater depression of the sulci. 



From E. cihoUensis, also from the Wasatch, it differs in having the 

 humeral-pectoral sulcus crossing behmd the entoplastron, and also 

 in being of much smaller size. 



Family TRIONYCHID^. 



ASPIDERETES LATUS. new species. 



Plate 37. 



Type.— 'No. 8802, U.S.N.M., consists of the carapace, which lacks 

 the nuchal, preneural, and first neural. Collected by Levi Sternberg, 

 1917. 



Type locality. — Sand Creek, Province of Alberta, Canada. 



Horizon. — Belly River formation, Upper Cretaceous. 



The turtle carapace described below is provisionally referred to the 

 genus Aspideretes, as the absence of the nuchal, preneural, and fii-st 

 neural renders a positive genus determination impossible at this time. 



Except for the loss of the parts mentioned this specimen is in an 

 excellent state of preservation. Certain peculiarities show it to be 

 an undescribed species, and the name Aspideretes latus is here pro- 

 posed. 



The carapace has been flattened by pressure so that its natural 

 transverse convexity has been largely eliminated. The shell is wider 

 than long, the greatest diameter across the third costals being 290 

 millimeters. It is estimated that the greatest length at the center 

 was about 240 millimeters. 



115690— 19— Proc.N.M.vol.56 9 



