178 O. C. Marsh — Notice of some Extinct Testudinata. 



Portions of two other skulls beside the type specimen are 

 preserved, and these afford several additional characters. 

 They belong apparently to the same species. 



There is a post-temporal arch. The occipital condyle is 

 nearly round, and has a deep pit in the center. The condyle 

 is formed entirely of the basioccipital, as the thin exoccipital 

 plates do not reach the articular surface. The basioccipital 

 processes are prominent, and directed backward. The ptery- 

 goids separate the quadrates and the basisphenoid. At their 

 union with each other, they are much constricted, but expand 

 in front. The quadrate is stout and curved, and its articular 

 face is deeply notched. 



The lower jaws referred to this species are slender and 

 much less sculptured than the skull. The dentary bones unite 

 at the symphysis by a short, open suture, and form a sharp 

 elevated point to meet the decurved tooth-like beak above. 

 The upper border is quite sharp, and fits well into the deep 

 alveolar sulcus of the maxillary. 



The carapace, represented in Plate VII, figure 2, was not 

 found with the skull, and may possibly represent a distinct 

 form. It resembles the corresponding part in Dermatemys, 

 but the costals do not meet on the median line. It has the 

 complete number of eight neurals, and in this and some other 

 characters resembles Iielochelys, von Meyer, from the Creta- 

 ceous Greensand of Germany, and I J leurosternon, of Owen, 

 from the English Purbeck. 



The plastron of a third individual had mesoplastral bones, 

 an intergular plate, and inframarginals, as in the above genera. 

 The pelvis was not coossified with the carapace or plastron. 

 The sculpture of both carapace and plastron is similar to 

 that of the skull. 



The present genus appears to be most nearly related to 

 Co7?ipsemys of Leidy, from the Cretaceous, but as the skull of 

 that genus is not known their more exact relations cannot at 

 present be determined. 



The specimens here described are from the Atlantosaurus 

 beds of the Upper Jurassic of Wyoming, and hence are among 

 the oldest known American turtles. They appear to represent 

 a distinct family which may be called the Glyptopsidoe. 



Adocus pimctatiis, sp. nov. 



The type specimen of this species is in part represented on 

 Plate VII, figure 3. The plastron belonging with the cara- 

 pace shown is also in excellent preservation. The skull is not 

 known. The structure of the carapace indicates that this 

 specimen is nearly related to that described by Leidy, under 



