IdXOCHELYlDiE. 



169 



B. F. Mudge, in the Niobrara deposits of Kansas, near the forks of the Smoky Hill River. 

 The animal was a large one, since the mandible, from the symphysis to the angle of the jaw, 

 measures 157 mm. In 1877, as cited in the synonymy, Professor Cope came into possession 

 of 2 nearly complete skulls, which he identified as belonging to T . latiremis, and these he 

 described. These skulls are now in the American Museum and bear respectively the numbers 

 1496 (fig. 202) and 1497 (figs. 203, 204). The latter (and probably both specimens) was 

 collected somewhere along the Smoky Hill River. A comparison of the lower jaws of these 

 skulls with that of the type makes it certain that the former were correctly referred. 



The first publisht figure of the skull of this species was made by Hay, as cited. This 

 skull lackt the lower jaw; but a comparison with the skulls described by Cope reveals no 

 differences. Other skulls have been figured by Case and Williston, as cited. 



This appears to have been the commonest turtle in the Niobrara beds of Kansas, yet many 

 parts of its skeleton remain unknown. The size attained was considerable. If the length of 

 the coracoid bore the same relation to the length of the carapace that subsists between these 

 bones in Chelydra 01 Caretta, the carapace must have been about a meter in length. It may be 

 remarkt here that the coracoid of Cope's type was 225 mm. long, that author's statement 

 that it was 250 mm. being incorrect. The ramus of the mandible has a length of 157 mm., so 

 that the skull, from the tip of the snout to the occipital condyle, was close to 160 mm. 



The skull of this species is broad posteriorly. 

 In front of the quadrates the width is gradually 

 reduced, so that the head is wedge-shaped and 

 the snout pointed. Altho all the skulls yet found 

 are considerably flattened by pressure, it is quite 

 certain that the head was rather deprest, more 

 like that of Chelydra than like that of any of the 

 living Cheloniidx. The supraoccipital is long. 

 The temporal region is rooft over about as in 

 Caretta. and the squamosal appears to have come 

 into narrow contact with the parietal. The orbits 

 lookt upward and outward, resembling more 

 those of ChelxJra than those of the Cheloniida?. 

 The opening of the anterior nares is large, con- 

 trasting strongly with that of T . stetwpora. The 

 tympanic cavity did not extend into the squa- 

 mosal, but had the stage of development seen in 

 the loggerhead. The cutting-edge of the maxilla 

 is moderately high anteriorly, but becomes very 

 low at the hinder end. As seen in profile, it is convex. There is a rough ridge on the palatine 

 near its articulation with the maxilla. The alveolar, or masticatory, surface of the upper jaw is 

 somewhat concave from side to side. Including the ridge on the palatine, this surface is not 

 so wide as is the fossa containing the choanae. There are large posterior palatine foramina. 

 The narrowest portion of the palate, across the pterygoids, is rather wide compared with the 

 other species, and is flat. More posteriorly each pterygoid bears a groove which is directed 

 outward and backward toward the hinder border of the quadrate. 



The lower jaw is relatively weak. The alveolar surface is narrower than in the other 

 species in which it has been observed. Fig. 205 represents the lower jaw belonging to 

 specimen shown in figures 203 and 204. The outer edge is sharp and rises somewhat above 

 the inner edge. The latter rounds "ft into the inner face of the jaw, which face is in no 

 way hidden by the surface referred to. At the symphysis the alveolar surface extends back- 

 ward little more than one-half as far as does the lower face of the bone. The tip of the jaw is 

 slightly beakt. 



Notwithstanding the fact that a considerable number of skulls of this species have come 

 to light, portions of the carapace or plastron are rare. Wieland (as cited) mentions portions 

 of the carapace and plastron in Yale University, but he does not describe them. 



The cervical vertebras and some caudals have already been described in the discussion 

 of the genus. No other vertebrae are known. 



Fig. 206. Toxochelys latiremis. Scapula and 

 coracoid. xi. Redrawn from figures by Case. 



