AND THREE ALLIED NEW GENERA. 



existing saurian ; they are pyramidal, with the outer side nearly plane, or slightly 

 convex, and separated by two sharp ridges from the remaining surface of the tooth, 

 which forms a half-cone (PI. I. Fig. 1); the transverse section of the tooth near its 

 attachment to the osseous base presenting the contour given at PL I. Fig 1. All 

 the teeth are slightly recurved, and their peripheral surface is smooth. They are 

 implanted upon the intermaxillary, maxillary, and ' premandibular bones. A series 

 of similarly shaped but much smaller teeth are placed upon the pterygoid bones." * 



The successional tooth pierced through the osseous body which supported the 

 primary tooth, and this became detached, together with its base, by a kind of ne- 

 crosis, and fell off, like the horns of a deer. 



There are fourteen teeth on each side of the lower jaw in the specimen in the 

 Paris Museum. In the upper jaw there are eleven teeth, but the intermaxillary 

 bone is wanting, on which Cuvier was induced to believe there may have been 

 three. On each pterygoid bone there seem to have been eight teeth. A cast of the 

 Maestricht Mosasaurus may be seen in the Cabinet of the American Philosophical 

 Society. 



The vertebrae of this saurian have the form of those of the living Crocodiles, 

 Monitors, and Iguanas, namely, they are concave anteriorly and convex posteriorly : 

 the anterior vertebrae have these characters more strongly marked. 



Of the vertebrse there are five sorts, based on the number of apophyses. The 

 first have an upper spinous apophysis, long and compressed ; a lower, terminated 

 by a concavity ; four articular, the hinder ones shorter and facing outwards, and 

 two transverse apophyses, bulky and short ; these are the last vertebrse of the 

 neck, and the first of the back : their body is longer than broad, and broader than 

 high ; the faces are of a transverse oval form. Others are without the lower 

 apophysis, but in other respects resemble the preceding. Some follow which have 

 articular apophyses ; these are the last dorsal, the lumbar, and the first caudal : 

 their peculiar place is recognized by their transverse apophyses, which are elon- 

 gated and flattened more and more ; the articular faces of their body are 

 nearly triangular in the first caudal. Those which follow have, besides their 

 upper spinous and the two transverse apophyses, two little facets at their lower 

 face to support the chevron-formed bone ; the articular faces of their body are 

 pentagonal. Then come others, differing from these in having no transverse 

 apophyses ; they form a large portion of the tail, and the faces of their body 

 are ellipses, at first transverse, and then more and more compressed at the sides ; 

 the chevron-bone is anchylosed, and forms a body with them, which is a peculiarity. 

 The vertebrse of the tail have no apophyses : in proportion as they approach the end 

 of the tail the bodies are shortened, and almost from its commencement they have 

 less length than breadth or height : the length of the last is one half its height. 



Next to the Mosasaurus Hoffmanni, the specimen described by Goldfuss is most 

 interesting, as the head is nearly perfect. These remains were found in the Creta- 

 ceous formation near the Big Bend in the Upper Missouri, by Major O'Fallon, 



* Owen, Odontography. 



