36 



HAY. 



[Vol. II. 



teeth, and their sizes and arrangement agree well with Cope's 

 figure of the dentary of this species presented by him {Cret. 

 Vert., JPl. XLIII, Fig. 3). Probably it will be well not to rely 

 too much on the number of the teeth as a specific character. 



Professor Cope states {Proc. Anic7'. 

 PJdlos. Soc, vol. xii, p. 175) that the 

 teeth of these fishes descend in their 

 alveoli to the depth of an inch. The 

 large teeth really have much longer 

 roots than thus indicated. In the 

 lower jaw the bases of the large teeth 

 near the symphysis descend nearly to 

 the lower border of the jaw. Fig. 4 

 presents a view one-half the natural 

 F.G. 4. -xiphactinus The mandible gJ2e of the symphyscal end of the 



near symphysis, with bone broken j i. j 



away to show the roots of the teeth, mandiblc of a spccics of Xiphactiuus, 

 ^ ^ seen from the outside. The bone has 



been broken away so as to expose the roots of the teeth, and 

 portions, too, of these are missing. The teeth in life had a 

 very large pulp, and the cavity containing this pulp had, since 

 burial, been filled up with crystallized calcite. This, in the 

 drawing, is stippled. Where the calcite has fallen out and 

 exposed the inner surface of the dentine the shading has been 

 made by perpendicular 

 lines. The broken edges 

 of the dentine itself are 

 shaded by horizontal 

 lines. j,„ 



Cope and Crook have 

 both figured the articula- 

 tion of the lower jaw with 

 the quadrate. It appears 

 to me that the figures of 

 both are more or less erroneous, or, at least, misleading. 

 Professor Cope {Crct. Vert., p. 194) states that the articular is 

 distinct, wedge-shaped, short, and supports half the cotylus. 

 He describes the angular as having a prominent angle, like 

 half an ellipse, and extending in a long sword-shaped process 



Fig. 5. — Xiphactinus. Proximal end of lower 

 jaw. X 5. 



