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ART. XXXI. — On Bathygnathus horeatis, an extiiict Saurian of the New Red 



Sandstone of Prince Edrvard's Island. 



By Joseph Leidy, M. D. 



In the last visit of the enthusiastic and distinguished geologist, Sir Charles Lyell, 

 to this country, he informed me that Mr. J. W. Dawson, of Pictou, Nova Scotia, had 

 received from Mr, D. McLeod, for disposal, a fragment of a jaw of a large saurian 

 animal, which was found in the New Red Sandstone Formation of Prince Edward's 

 Island. Mr. Lyell sent me an outline drawing of the jaw ; and with the disinterest- 

 edness of a cosmopolite philosopher, recommended Mr. Dawson to send the specimen 

 to the Academy of Natural Sciences of Philadelphia, in preference to disposing of it 

 abroad. It was accordingly sent to the latter place, and was purchased by Messrs. 

 Isaac Lea, William S. Vaux, and myself, and was presented to the Academy, in 

 the cabinet of which it is now very appropriately arranged at the side of the only 

 other known saurian bones discovered in the New Red Sandstone of North America, 

 described by Mr, Lea, under the name of Clepsysaurus Pennsyhanicus. 



The specimen consists of the right dental bone, considerably broken, attached by its 

 inner surface to a mass of matrix of a red granular sandstone, with large, soft, angular, 

 red chalk-like stones imbedded in it. The fossil has seven large teeth protruding be- 

 yond the alveolar margin 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 alacertian 

 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 in figure 1, 

 plate xxxiii., is five inches, whilst its length in the perfect condition appears not to 

 have been moi*e than 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 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 inferiorly above the base of the bone is depressed 

 ifito a moderately deep concavity. The upper or alveolar border forms a convex line 

 rapidly descending towards the chin. The base forms an oblique line, and ascends 

 anteriorly to the chin; and it appears thick and rounded externally ; but in 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 its usual 

 position in saurians 



