SYSTEMATIC REVISION OF THE SUBORDER. 63 



INCERTAE SEDIS. 



Bathygnathus borealls Leldy. 



Jnl. Acad. Nat. Sc. Phila., (2) vol. 11, 1854, p. 327, plate 33. 

 Am. Jnl. Sc, (2) vol. xiv, 1855, P- 444- 



Type : The left maxillary, incomplete above, but with the alveolar edge preserved 

 from the maxillary-premaxillary suture to near the posterior end ; several teeth pre- 

 served entire. From the vicinity of New London, Prince Edward Island, Canada. 

 Preserved in the museum of the Philadelphia Academy of Science. 



Leidy considered that tlie bone was the lower jaw instead of the upper; 

 this accounts for the name and for the terminology of his description. 



Original description : " The specimen consists of the right dental bone consider- 

 ably broken, attached by its inner surface to a mass of matrix of red granular sand- 

 stone, with large, soft, angular, red chalk-like stones imbedded in it. The fossil has 

 seven large teeth protruding beyond the alveolar edge of the jaw ; and it is hard, brittle, 

 and cream-colored, 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 below the contiguous pair of equal sized teeth 

 * * * is 4 inches, while its length in the perfect condition appears not to have 

 been more than ■]),{ 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 neighboring bones. 



" The outer side of the jaw is vertical and over the course of the alveolar parapet 

 is plane; but below this posteriorly and interiorly above the base of the bone is 

 depressed into a moderately deep concavity. The upper or alveolar border forms a 

 convex line descending rapidly toward the chin. The base forms an oblique line and 

 ascends anteriorly to the chin; and it appears thick and rounded externally; but on 

 the specimen it presents an abrupt border internally, as if the inner side of the bone 

 had been broken away, or as if the angular bone had articulated with it, much in 

 advance of the usual position in saurians. 



" The external surface of the dental bone is everywhere marked by fine, reticular, 

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

 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 Iguanas, Varanus, etc., but near the point of the chin there is a rela- 

 tively very large foramen, partially filled with matrix, which appears to correspond 

 with the internal mental foramen of the Iguana. [This is the nostril.] 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, are placed on the inner side, and rest 

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

 parapet is supported between the teeth, as in Megalosaurus, I can not certainly 

 ascertain from the inner side of the jaw being so closely adherent to the matrix. The 

 dental bone is to be considered complete in its length in the specimen, is capable of 

 containing a series of 12 teeth posterior to and including that most anteriorly situated 

 in the fossil. 



