293 



The specimen consists of a fragment of the ramus of a U)\ver jaw con- 

 taining a numl)er of teeth. Four principal teeth and part of the attachment 

 of another are retaineil in the fragment. These teetli are ranged oblicpiely 

 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 7i lines wide by 2| lines fore and aft, and they successively increase in 

 breadth to the last, which measures 8| lines wide by 2j|- 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 2J lines in diameter fore 

 and aft and IJ lines transversely; the last one is 3 J fines by 2 fines. 



The jaw-bone internal to the teeth just described rises in a ri<lge 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 smaUer 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 tln^ row is preserved, 

 and this is transversely ovoid, with tlie 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 tlie 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 simihir to the largest 

 ones above described. 



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

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

 Natural Sciences of Philadelphia for 1857, p. 1G8, under the name of 

 Pycnodus rohustus. 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 mucli larger. Its long diameter is 14^ lines, and its short 

 diameter nearly 4 lines. 



