42 FOSSIL REPT1LIA OF THE 



the same acrodont type of dentition as in Mosasaurus and Geosaurus, but differed in 

 their closer arrangement and from the former, especially, in the shape of the crown, of 

 which the outer side was as convex as the inner side, the transverse section being an 

 ellipse with pointed ends, which latter corresponded with two opposite trenchant edges 

 dividing the outer from the inner side of the crown. This was covered by a smooth 

 enamel without any indications of minor ridges or facets : the apex of the crown was 

 sharp-pointed ; the body of the crown slightly recurved ; and its base expanded into 

 a thick fang of a circular form, which was anchylosed to a short conical process of 

 the alveolar border of the jaw. 



Deducing the generic dental characters of Mosasaurus from the magnificent 

 example of the jaws and pterygoid bones, which passed from Dr. Hoffmann's 

 collection to that of the Canon Goddin, and ultimately to the Museum of the Garden 

 of Plants at Paris, the deviation in the teeth in question from the inequilateral facetted 

 character of the crowns of the maxillary and mandibular teeth of that specimen was 

 so great, as to lead me to infer that these teeth from the English chalk belonged to a 

 distinct genus of the same family of the Lacertine order ; unless, indeed, they might 

 be pterygoid teeth of a species of Mosasaurus, distinct from the Mosasaurus Hoffmanni. 

 After a rigid comparison in reference to this question, I was led to the conclusion 

 that they were not pterygoid, but maxillary teeth, and I therefore described them 

 under the name of Leiodon anceps. The general results of that comparison, which 

 would have been out of place in a systematic Treatise of Teeth in general, will here 

 be requisite. 



Leiodon anceps, Owen. Tab. IX, A. 



' Odontography,' 1840, vol. i, p. 261 ; vol. ii, pi. 72, figs. 1 & 2, 

 Mosasaurus stenodon. Charlesworth. The London Geological Journal, 1846, p. 23. 



pis. 4 and 6. 



Baron Cuvier, after a close and accurate description of the pterygoid bones of the 

 great Mosasaurus Hoffmanni, concludes by stating, that " each of these bones seemed 

 to have supported eight teeth, which grew, became attached, and were replaced, like 

 the teeth of the jaws, but were much smaller."* They also differ from the jaw-teeth 

 by having their two sides less unequal in regard to their convexity ; the inner side is 

 almost as convex as that side of the maxillary teeth, but the outer side of the 



* " Cet os paroit avoir porte dans notre animal fossile huit dents qui croissoient, se fixoient et se 

 remplacoient comme celles des niachoires, quoique beaucoup plus petites." (Ossemens Fossiles, torn, v, 

 pt. ii, p. 324, 4to, 1824.) 



