218 



NORTH-CAROLINA GEOLOGICAL SURVEY. 



cated as existing upon the outer face in his transverse section, 

 but that those faces are concave has not been stated by any 

 writer. 



The transverse section of the tooth, Mossosaurus Hoffman i, 

 given by Prof. Owen, has no angularities at all on either 

 face the figure of the M. Maximiliani exhibits them upon 

 the anterior face, but none upon the inner. 



The tooth which I have just described is perfect, and not 

 worn ; the figures are good illustrations of its characters, and 

 it appears, therefore, that the characters are either not uniform 

 or else there are two species belonging to the green sand. It 

 is evident that the tooth in question belongs to the species, 

 Maximiliani, rather than the lioffrnani or gracilis. 



Fio. 37. (A.) 



POLYGONODON RECTUS, LEIDY. MOSSOSAURUS RECTUS. 



Tooth long, pointed, compressed; near- 

 ly equally divided on the outer and in- 

 ner faces ; the faces are formed by five 

 equal and similar planes, bounded by 

 angular ridges, only two of which, on 

 each face, can be said to approach the 

 apex ; these are the two anterior and tw r o 

 posterior ridges curved backwards ; bi- 

 carinate ; but the posterior edge is near- 

 ly straight, while it has a convexity be- 

 fore which gives an apparent curvature 

 which does not exist ; edges smooth ; 

 enamel is probably thin or removed, 

 leaving a dense dentine, with fine longitudinal cracks which 

 appear at first like fine striae. The tooth is broken at the 

 base of the crown, showing a shallow pulp cavity. 



This tooth differs from any of the preceding in its form and 

 surface. It is particularly noticeable, that the part near the 

 base is distinctly angular, and is divided into ten nearly equal 

 planes, and is bounded by well defined angles. All these 

 angles extend a little above the middle of the tooth. It dif- 

 fers from either of the three species of Mossosausus in its pro- 

 portions. It also differs from the teeth of the Leiodon, by be- 



