140 



of an anterior cervical is little, or not at all, distorted, as are also many of the 

 caudals. All the dorsals and cervicals have transversely-oval articular faces, 

 openly notched above for the neural canal. The fixed hypa]3ophyses arc 

 large ; the last one small and subconic, abruptly following a large truncate 

 one. The three succeeding dorsals are keeled below, the keel of the last 

 low and obtuse. The zygosphen is weak, and deeply notched in the middle. 

 On the anterior cervicals, it is rudimental; but, on the dorsals, supports a well- 

 developed articular facet, which meets a corresponding one of the zygantrum. 

 The fixed hypaj^ophyses and roofs of the posterior zygapophyses are rugose, 

 with grooves and ridges. The articular faces of the caudals are broad, 

 vertical ovals as far as the specimens extend, the series including only a part 

 of those with diapophyses. On the anterior caudals, the chevron-facets are 

 compressed. The neural spines are thinned out in front; obtuse at tiic base 

 behind, but expanding to a thin edge there also. The sides are longitudinally 

 grooved. Diapophyses on the middles of the sides. Some ribs have tiie 

 heads not expandad but truncate. The angle of the mandible is produced 

 backward, and below the plane of the lower margin of the ramus, in a marked 

 manner. The lower margin and the surface next the smooth edge are 



rugose. 



Measurements, 



M. 



Depth of the mandible at the posterior margin of the cotyliis 0. 058 



Length of the centrum of the anterior cervical 0. 070 



Diameter of the ball, vertical 0. 028 



Diameter of the ball, transverse 0. 040 



E.\i>an8e of the diapophyses of the anterior cervical 0. 09.") 



Expanse of the anterior L'ygapophyses - 0. 064 



Expanse of the diapoi)hy8es of the anterior dorsal 0. 115 



Length of the centrum of the anterior dorsal 0. 071 



Length of the centrum of the anterior caudal 0. 053 



Depth of the cup of the anterior caudal 0. 044 



Width of the cup of the anterior caudal 0. 041 



Width of the neural spiue 0. 03;i 



Elevation of the neural si)ino (apex lost) 0.070 



Diameter of the centrum of the twenty-fourth caudal, vertical 0. 039 



Diameter of the centrum of the twenty-fourth caudal, transverse 0.040 



Length of the centrum of the twenty-fourth caudal 0. 042 



This species appears to have had proportions not unlike those of Plate- 

 carpus coryphceus ; the specimen described being larger than that on wliich the 

 latter was based. It is also ratlicr larger tlian the Clidastes planifrons, Cope, 

 llic largest of its genus, Init which, since its caudal vertebfie are unknown, may 

 yd Ik; I'ouiid to he a Sironectes. It differs specifically fruiu the S. angullferus 

 ill llic less (Icscliipinciit of I he zygi)s[>iicii, especially im I he aiilciior verlebtje, 



