COPE.] PALEONTOLOGY CEETACEOUS PERIOD VEETEBEATA. 453 



Jleasuremeyits. 



M. 



Length of fragment of ramus 100 



Width in front 034 



Depth behind 032 



Length of eight alveoli 069 



Diameter of largest alveolus *. 012 



Diameter of smallest „ '. 007 



Width of base of angle of ramus 048 



Depth at surangular 034 



Length of centrum of vertebra 045 



Width of articular cup 031 



Vertical diameter of cup 025 



Vertical diameter of neural arch Oil 



Expanse of anterior zygapophyses 056 



The specimen is adult, and indicates an animal about the size of the 

 alligator of the Southern States. Its reference to the present genus is 

 provisional only. 



TESTUDINATA. 

 TRIONYX, Geoifr. 



Trionyx vag-ans, sp. nov. ; Trionyx'^. foveatits, Leidyj Proceed. Acad. 



iifat. Sci. Philadelphia, 1856, 312. 



Eepresented by a number of fragments of costal bones and perhaps 

 of steruals also. The former are rather light or thin for their width, 

 and are marked with a honey-comb i)attern of sculpture, in which the 

 ridges are thin and much narrower than the intervening pits. They in- 

 cline to longitudinal confluence at and near the lateral sutures. Several 

 aresB are not infrequently confluent in a transverse direction near the 

 middle of the bone. 



Measurements. 



M. 



Width of costal bone 0370 



Thickness of costal bone 0045 



Four and five arese in 0™.010. 



This species difl:ers from the T.foveatus, Leidy, in the much narrower 

 interareolar ridges, and larger arese, and in their longitudinal confluence 

 at the margins, characters exhibited by numerous specimens. 



Lignite Cretaceous of Colorado; near the mouth of the Big Horn 

 Elver, Montana ; Long Lake, Nebraska 5 found at the last two localities 

 by Dr. Hayden. 



PLASTOMENUS, Cope. 



Annual Report U. S. Geol. Survey, 1872, 617. 



Plastomenus (?) PUNCTULATUS, sp. nov. 



Established on a costal bone found in association with the preceding 

 species, and referred to the geniis Flastomcnus provisionally, and with a 

 probability that it will be found not to pertain to it when fully known. 

 That genus has so far only been found in the Eocene formation. The 

 bone is rather thin and suificieutly curved to indicate a convex carapace 

 of moderate thickness. The surface is marked with closely-packed shal- 

 low i^its without material variation of form on the proximal half of the 

 bone. The result is an obsolete sculpture quite similar to that seen in 

 some species of the genus to whicli it is at i^resent referred. 



