AND AYES OF NORTH AMERICA. 



223 



Length of sixth cervical, neural arch, 

 Width at narrowest point of " " 

 Expanse of zygosphens, 



" " zygapophyses (anterior), 

 " diapophyses, 

 Width cup, 



Depth centrum and both hypapophyses, 

 Length free hypapophysis, 



" centrum (inol. ball) of twenty-third V., 



" neural arch, 



" between anter. zygapoph. and diapoph. 

 Depth diapophysis, 



" neural arch and centrum, 

 Width centrum (least), 



" ball, 

 Depth " 



Length of an anterior caudal (no diapoph.), 

 Width cup, 

 Depth, 



Total depth centrum and spines, 

 Neural spine and arch, 

 Antero-posterior width base spine, 

 Length of 18th caudal from the last, 

 Width caip, 

 Depth " 



Length distal caudal. 

 Width cup. 



Depth " 



Lilies. 

 IS. 6 



8 



4 



18.3 

 19 



8.5 

 14.8 



5 



16.8 

 16.fi 



7 



5.8 

 14 

 7.5 

 9.8 

 7.8 

 7.3 

 8 

 7 

 .54.8 

 16 

 7.2 

 5.8 

 7 



5.8 

 8.4 

 2.;! 

 8. 



The form of the crcmiwm is that of an elongate Mat, wedge. The lateral outlines arc slightly contracted just be- 

 hind the anterior opening of the nostrils. A deep emargination occurs at the orbits, while the temporal fosssB inter- 

 rupt the outline more deeply still. The projection of the opisthotic and squamosa] is about as extensive as that of the 

 post-frontal. Throughout, the surface from muzzle to occiput is quite plane, though the latter region has been evi- 

 dently slightly crushed, and the posterior median frontal region is slightly concave. Transversely, there is a strong 

 concavity, with vertical inner margin on each side, the median parietal region. The posf-frontals are slightly decurved, 

 the pre-frontals still less so. The nasal region would be plane transversely hid. for two shallow longitudinal grooves, 

 separated by alow raised line which extends from the middle of the front along tin; nasal septum. 



A section of the muzzle in front of the nostrils would In', a semi circle; posterior to this point the sides of I, he 



maxillaries are more vertical. The edges of the projecting orbital bones are thin, as well as the orbital rim of the 



frontal. The Inner margin of the maxillaries is very thin and rolled over the outer margin and extremity of the thin 



pre-frontal. The bones are all relatively more fragile than in Mosasaurus, 'the posterior process of the post-frontal. 



which is received into a. groove on .the inner fa.ee of the squamosal, is sub-trigonal. 



The parietal crests arc the lateral angles above mentioned. They are nearly parallel behind, and diverge gently 

 in front; they then diverge still more, and extend along the suture between the parietal and frontal bones, and then 

 disappear. There are no other ridges on the cranium, except tin! median occipital, which is low. 



The premaxillary and anterior maxillary leeth arc more rounded than the posterior maxillaries. The former have 

 an angle separating inner and outer planes, in front only, the latter, commencing at the sixth maxillary, on both an- 

 terior and posterior lines. In the tooth named, till! inner face is the more convex and extensive; there arc no facets 



