164 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. XXXV. 



diagonally by one prominent, narrow, and sharp ridge and by a num- 

 ber of less conspicuous ridges. As a result, the surface has a very 

 uneven appearance. The peripherals also are, or have been, similarly 

 sculptured. As shown by the tenth and eleventh (Plate XXVII, fig. 1 ) , 

 the area in front of the descending sulcus is ornamented by ridges 

 nearly parallel with the sulcus, while the area behind it has grooves 

 and ridges running downward and backward. A somewhat similar 

 sculpture is observed on a specimen of Pseudemys rubriventris. 



This species appears to be most closely related to //. crassa (Cope), 

 fully described and figured in the writer's forthcoming monograph. 

 This species was described by Cope from the Lower Eocene of New 

 Mexico, but whether from the Puerco or the Torre j on is uncertain. 

 From this II. calata differs in having the bones strongly sculptured; 

 also apparently in having the peripherals more closely sutured to the 

 costals and less concave outwardly. 



ECHMATEMYS RIVALIS, new species. 



The turtle which forms the subject of this description is repre- 

 sented by a damaged shell which was found by Mr. E. E. Smith, of 



the U. S. Geological Survey, in 

 1907, on the line between sections 

 10 and 20, township 23 north, 

 range 93 west, in what is known 

 as the North Rawlins coal field, in 

 the eastern part of Sweetwater 

 County, Wyoming. I am in- 

 formed by Dr. T. W. Stanton 

 that the beds in this region belong 

 to the Wasatch, or are at most 

 not older than the Wasatch. This 

 conclusion is confirmed by this 

 turtle. This specimen, now in the 

 IT. S. National Museum, is Cat. 

 No. 5781. The parts of the shell 

 preserved are shown by the figures. 

 The total length of the cara- 

 pace (fig. 2), in a straight line, 

 was originally close to 260 mm.; 

 the breadth close to 190 mm. The 

 nuchal bone has its hinder parts 

 wanting. The free border has a 

 width of 40 mm. It is conspicu- 

 ously notched on each side of the nuchal scute. The first, second, 



Fig. 2. 



-Portion of carapace of Echma- 

 temys rivalis. 



° Fossil Turtles of North America, p. :_'<;:!, pi. xxxvni, figs. 4-9, text-tig. 325. 



