293 



The specimen consists of a fragment of the ramus of a lower jaw con- 

 taining a number of teeth. Four principal teeth and part of the attachment 

 of another are retained in the fragment. These teeth are ranged obliquely 

 parallel with one another from within backward and outward. In outline 

 they are elongated-bean shaped, being slightly concave in front and convex 

 behind, and slightly wider externally than internally. The first of the series 

 is 7£ lines wide by 2f lines fore and aft, and they successively increase in 

 breadth to the last, which measures 8f lines wide by 2f lines fore and aft. 



At the bottom of the slope, to the inner side of the large teeth, there is a 

 row of three smaller teeth and the traces of attachment of a fourth one. 

 The three teeth, like the others, successively increase in size from before 

 backward. They are ovoid, and situated obliquely nearly opposite the inter- 

 vals of the large teeth. The first of the series is 2-£ lines in diameter fore 

 and aft and 1£ lines transversely; the last one is 3£ lines by 2 lines. 



The jaw-bone internal to the teeth just described rises in a ridge toward 

 the symphysis. The slope at the fore part of the ridge exhibits the attach- 

 ments of two minute teeth, indicating a second row internal to the largest 

 teeth. 



To the outer side of the latter the specimen retains evidences of two rows 

 of smaller teeth. Of these, the first row shows remains of seven teeth in 

 the length of space occupied by the five principal teeth, and, like these, they 

 successively increased in size. Only the fourth tooth of the row is preserved, 

 and this is transversely ovoid, with the long diameter 2 lines wide and the 

 short diameter If lines. 



Fig. 15, of the same plate, represents a specimen apparently from the same 

 species, belonging to the Museum of the Academy of Natural Sciences of 

 Philadelphia. It was presented by Dr. J. H. Slack, who obtained it from the 

 green sand marl of Crosswicks, Burlington County, New Jersey. It consists 

 of a small jaw-fragment containing three broad teeth similar to the largest 

 ones above described. 



An isolated tooth from New Jersey, submitted to my inspection by 

 Professor Gr. H. Cook, is noticed in the Proceedings of the Academy of 

 Natural Sciences of Philadelphia for 1857, p. 168, under the name of 

 Pycnodus robustus. The specimen represented in Figs. 18, 19, Plate 

 XXXVII, has the same shape as in the largest teeth of those referred to 

 P. faba, but is much larger. Its long diameter is 14£ lines, and its short 

 diameter nearly 4 lines. 



