120 THE TRIAS OR NEW RED SANDSTONE. 



imbedded in it.* The fossil has seven large teeth protruding beyond 

 the alveolar margin of the jaw; and it is hard, brittle, and cream- 

 coloured, and stands out in beautiful relief from its dark-red matrix. 

 The jaw indicates a lacertian reptile, and, in comparison with that of 

 other known extinct and recent genera, is remarkable for its great 

 depth in relation to its length. 



"The depth of the dental bone is five inches, whilst its length 

 in the perfect condition appears not to have exceeded seven and a 

 quarter inches ; for in the specimen the middle part of the posterior 

 border is so thin and scale-like, that I am disposed to think it here 

 came in contact with the supra-angular and other neighbouring bones. 



" The teeth, in their relation to the dental bone, are placed on the 

 inner side, and rest against the alveolar border, which rises in a 

 parapet external to them. Whether this parapet is supported by 

 abutments between the teeth, as in Megalosaurus, I cannot clearly as- 

 certain, from the inner side of the jaw being so closely adherent to the 

 matrix. The dental bone, if it be considered complete in its length 

 in the specimen, is capable of containing a series of twelve teeth. 



" As the teeth were worn away or broken off, they were replaced 

 by others produced at their inner side, as is indicated in the specimen 

 by a young tooth, which is situated .internal to, and is concealed by, 

 the largest mature tooth. The enamelled crowns of the fully pro- 

 truded teeth are exserted at their base for several lines above the 

 alveolar border of the jaw. They are compressed, conoidal, and 

 recurved ; but compared with those of Megalosaurus they are not so 

 broad, compressed, nor recurved, and they are more convex externally, 

 and are less so internally. They resemble much in form those of the 

 recent Monitor ornatus, but are less convex internally. The anterior 

 and posterior acute margins of the crowns are minutely crenulated ; 

 and the crenulations commence just below the tip, and descend as far 

 as the enamelled base." 



Dr Leidy then proceeds to describe the teeth minutely, remarking 

 that the first in the series is narrow, and not crenulated, and that it 

 is separated from the second by a space sufficiently large to have held 

 another tooth. " The second tooth seen in the figure is the largest 

 and longest of the series; and its enamelled crown, when perfect, was 

 about an inch and three quarters long by seven lines in breadth at the 

 base. Its fang can be seen in the wide fissure of the jaw, descending 

 two inches from the alveolar border; and, being broken, it is observed 

 to be hollow as far as the enamelled crown." The third tooth lias 

 not fully protruded, and the fourth, fifth, and sixth, have nearly the 

 * These are probably concretions. — J. W. D. 



