137 



tcrior zygapopliyscs. The inferior surfaces of the centra display a more or 

 less prominent longitudinal median ridge. 



Measurements. 



M. 



Length of the frontal bono to tho narea 0. 150 



Width of tho frontal bono i)08tcriorIy 0. 110 



Width of the frontal bono at thu orbits 0. 104 



Width of tho frontal bono at tho uares 0.040 



Width of tho palatine at the third tooth in front of tho transverse process 0.037 



Width of the palatine just behind tho transverse process 0.035 



Depth of the mandible at tho cotylus 0.040 



Depth of tho splenial condyle 0.032 



Width of the proximal articular surface of the quadrate (transVerse) 0.023 



Width of the distal articular surface »*^ fjiri"^ 



Length of the third cervical centrum 0. 0G2 



Depth of the ball of tho third cervical centrum 0.030 



Width of the ball of the third cervical centrum 0.037 



Length of tho articular end of the fixed hypapophysis 0.025 



Length of tho free hypapophysis 0.029 



Length of a median dorsal centrum 0.072 



Width of tho ball of a median dorsal centrum 0.048 



Dei)th of the ball of a median dorsal centrum 0. 040 



This species need only be compared with the Clidastes stenops, Cope, 

 which exhibits the same peculiarity of roof-shaped prefrontal bones. That 

 species has the cervical articular faces entirely round ; the frontal bone is 

 keeled in the middle, and the palatine much more vertically comjiressed. 

 The quadrate bone differs in various respects ; among others, in the round 

 form of the stapedial pit. As compared with the species described by Pro- 

 fessor Marsh as Edestosaurus dispar and E. velox, it differs in the form of the 

 (piadrate, which, in these species, is much as in C. tortor and C stenops; i. e., 

 with sliort proximal hook, oblique inferior articular surface, round pit, &c. 

 In this species, the quadrate is truncate distally, &c. This fine s^jecies was 

 discovered by the veteran geologist, Prof. B. F. Mudge, during his annual 

 expedition of 1873. 



AA. Centra of anterior dorsals compressed. 



Clidastes cineeiarum. Cope. 



The largest species of tliis genus, as indicated by the zygosphen articu- 

 lation of the vertebrae. 



The region whore it was foimd is (he same as the last, but the speci- 

 mens were taken from I ho gray bed, perhaps thi^ santc that ]ir<tdiiced llie 

 Elasmosauius platijurus, Copo. They consist of vcrtcbriu and iilcryiroid 

 18 c 



