DERMATEMYDID^. 



277 



No. 6110 has been a slightly smaller individual. Fig. 348 represents the front lobe of the 

 plastron. It is somewhat more pointed in front than that of the type. What is most interesting 

 is the presence of portions of the gulo-humeral sulci. The extent and position of these are shown 

 in the figure. The presence of these indicates that there has occurred in this genus a coales- 

 cence of the gulars and the numerals. 



Fig. 349 represents the right humerus seen from the dorsal surface. The general form is 

 that of the humerus ofChelydra. 



Baptemys iluviatilis sp. nov. 

 Plate 42, figs, i, 2; teit-figs. 350, 351. 



This species is based on a chelonite which was presented to the American Museum of 

 Natural History by Mr. Sidney Dillon, of New York City, in 1879. It is said to have been 

 obtained by him in Colorado, but there is no record of the exact locality, nor of the formation 



FIGS. 350 AND 351. Baptemys fluviatilis. Carapace and plastron of type. Xj. 

 350. Carapace. Restored costal and vertebral scutes indicated by interrupted dotted bands. 351. Plastron. 



from which it was derived. The specimen probably belongs to the Bridger formation and 

 there may be some error regarding the region. 



The specimen consists of a mass of gray sandstone, broken into two pieces, which bears 

 considerable portions of the carapace and impressions of other portions and a fragment of the 

 plastron, together with an impression of the inner surface of practically the whole plastron. 

 While we must regret the absence of many parts which might evidently have been preserved, 

 there is enough of the shell present to furnish us with the essentials of the structure. 



This shell has a length of 438 mm. and a width of 3 1 2 mm. The carapace (plate 42, fig. I ; 

 text-fig. 350) forms a high vault which rises from the lower surface of the plastron about 



