SAUROPTERYGIA. 235 



of the skull, are much narrower in Simosaurus than in Nollw- 

 or Pisio-saurus. 



The profile of the skull rises from the internasal to the 

 interorbital regions much more than in the Nothosaur, and 

 the depth of the skull behind the orbit is greater in propor- 

 tion to its length. The post-frontals are most clearly produced 

 backwards, along the upper border of the zygoma to the mas- 

 toids. The malars are co-extended, and connected with the 

 post-frontals, but terminate freely and obtusely a little beyond 

 the co-prolonged hind part of the maxillary, without being 

 met by or joining a squamosal. 



Most complete and extensive is the ossification of the roof 

 of the mouth in this genus. The pterygoids are expanded 

 into one broad unbroken imperforate flat expanse of bone, 

 from about one-third of the distance from the snout to the 

 occipital condyle ; they are united by a median suture, and 

 unclerlap the whole of the sphenoid. The teeth, compared 

 with Nothosaurus, are few and large, and are subequal, save 

 one or two at the fore and hind extremity of the series. The 

 crown expands a little above the fang, is conical, and im- 

 pressed by a few coarse longitudinal ridges : some teeth are 

 obtuse, others acute ; but all are shorter and thicker than in 

 Notho- or Pisto-saurus. 



The vertebras have flat or very slightly concave articular 

 surfaces on the body ; the neural arch articulates therewith 

 by suture. In these characters, and in their general propor- 

 tions, they resemble those of XotJw- and Plesio-saurus. It is 

 significant of some difference in respect of the arrangement of 

 the vertebras in the same column, that although specimens 

 from the tail, and from different parts of the back, have been 

 obtained, no cervical vertebra with any probability belonging 

 to this genus has yet been found. The caudal centrum presents 

 two well-defined, rather prominent, hypapophyses for the 

 haemal arch. 



