328 LEIDY ON BATHYGNATHUS BOREALIS. 



The external surface of the dental bone is every where marked by fine, reticular, 

 vascular grooves, and in the vicinity of the alveolar border it presents nunierous minute 

 vasculo-neural foramina. 



There is no regular row of foramina, visible in the specimen, for the transmission 

 of terminal branches of the inferior dental nerve, such as exists in the I|iuanas, Varani- 

 ans, etc., but near the point of the chin there is a relatively very large foramen, par- 

 tially filled with matrix, which appears to correspond with the internal mental foramen 

 of the Iguana. Just posterior to this foramen there is a deep vascular groove, which 

 in the perfect condition of the specimen may have proceeded from another foramen. 



The teeth in their relation to the dental bone, are placed upon the inner side, and 

 rest against the alveolar border, which rises in a parapet external to them. Whether 

 the parapet is supported by abutments between the teeth, as in Megalosaurus, I cannot 

 certainly ascertain 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 posterior to and including that most 

 anteriorly situated in the fossil. 



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 enameled crowns of the fully protruded 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, com- 

 pressed, 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 transverse section of the crowns of the teeth, except that of the first, is antero- 

 posteriorly elliptical, with the inner side less convex, and the extremities acute and in 

 most instances slightly incurved. 



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. 



In comparison with the teeth of Ckpsysaurus Pejinsylvanicus, those of the fossil 

 under examination are broader and more compressed, and except the first one of the 

 series, present an acute, crenulated margin anteriorly and posteriorly, whilst in the 

 former animal they are acute and crenulate only posteriorly. 



The crown of the first tooth represented in figure 1, plate xxxiii., slightly dislocated 

 anteriorly from its true position, is narrower than the other teeth, and is less com- 

 pressed. Its anterior border is obtuse and not crenulated, while the posterior border 

 is acute, but is too much broken to judge whether it was crenulated. This tooth is 

 situated three and a quarter inches above the base of the dental bone, and the ena- 



