SkeUton of a large Plfsionanr. 409 



from before bark wards and extending some distance bebind 

 tbe orbit. Tbe upper teetb seem to have had a slight 

 anterior and posterior carina, but otherwise their crown, 

 which is circular in section, is nearly smooth. 



7/ie Mandihle. — Like tlie skull the mandible is, unfortu- 

 nately, very incomplete. On the right side the ramus is 

 preserved as far back as the end of the dentigerous portion ; 

 on the left side, while much of the middle portion of the 

 ramus is wanting, the massive articular and angular region 

 is preserved. 



The syniphvsial region is greatly widened out, the expan- 

 sion exten(ling a little liebind the symphysis to the socket 

 of the sixth tooth. The splenials extend a short distance 

 into the symphysis, the ventral surface of which is much 

 roughened and perforated by numerous vascular foramina. 

 Behind this expanded portion the ramus is comparatively 

 slender. The articular region is extraordinarily massive, 

 and has tlie distal portion of the quadrate still articulating 

 with it ; the angular process is broken away. The anterior 

 ex|)ansion of the mandible bears six teeth on each side. 

 The anterior tooth is comparativeh' small, and is followed by 

 four large ones, the sixth being again small. Behind the 

 expansion there were about twenty-five small teeth — these 

 diminish in size towards the back of the jaw ; in several 

 cases alternate sockets are empty. The croMns of the 

 teeth are circular in section, and tlieir enamel surface 

 bears numerous sharp plications running towards the top of 

 tlie crown. 



Vertebral Column. — The cervical region is represented by 

 nine separate centra, free from the matrix and wanting 

 the arches, and four united with one another, with the arches 

 and zygapophyses present, but the neural spines lost : the 

 last of these seems to be the posterior cervical, the rib-head 

 having a slight contact witli the incipient diapophysis of 

 the neural arch. The atlas and axis are lost. The centra 

 of the ccrvicals are much shorter than wide, and a little 

 wi<ler than high. The length of the centrum in the mid- 

 ventral line is rather greater than at the neural canal. 

 The nearly circular articular surface is moderately deeply 

 concave, and its edges arc rounded off. The facets for the 

 ribs are distinctly divided into an upper and a lower portion 

 by a ridge. The ventral surface between the rib-facets is 

 perforated by a pair of large foramina separated by a 

 rounded liiemal ridge. 



Tiie neural arches are massive, an<l the zygapoj>hyses are 

 very large, with nearly circular articular stirfaccs which 



