180 DR. A. s. wooDAVAED ON EXTINCT [Mar. 5, 



clear that they are gently recurved, and fragments show that the 

 anterior border is serrated for more than half its length below the 

 apex at least in the first and third teeth. Xo successional teeth 

 are visible. 



Of the maxilla (mx.) only the oral border and some of its teeth 

 remain. That of the right side is most extensively preserved, and 

 bears seven of its teeth in a rather fractured state. Its outer face 

 is flattened and does not exhibit any large vascular foramina. Its 

 inner face does not bear any palatal extension. The teeth are 

 arranged in a moderately spaced series, and fixed in distinct sockets, 

 of which the inner wall is as much elevated as the outer wall and does 

 not exhibit any vertical clefts. All the teeth are much laterally 

 compressed, with a median indentation on each side near the base; 

 and their long diameter exactly coincides with the long axis of the 

 maxilla. The apex of the fully extruded teeth is much recurved. 

 The raai'ginal serrations, as in the premaxillary teeth, are disposed 

 at right angles to a tangent to the border ; and in the fifth tooth 

 at least they are shown to extend for considerably more than half 

 the length of the anterior border from the apex. The posterior 

 border of the fourth tooth displays serrations as far as its base. 

 The middle teeth are especially large and elevated, the height of 

 the fourth and fifth being about one and two-thirds times that of 

 the fourth premaxillary tooth. All the teeth, indeed, are larger 

 and more laterally compressed than those of the premaxilla. 

 Successional teeth are shown to arise at the inner side of the base 

 of the functional teeth. One has just displaced the third maxillary 

 tooth on the left, and another the seventh maxillary tooth on the 

 I'ight ; while the second right maxillary tooth is not completely 

 extruded. No other successional teeth are seen. 



Tlie mandible is represented only by its anterior half or dentary 

 region, which is nearly similarly preserved on both sides. The 

 rami must have been very loosely united at the symphysis, the 

 symphysial facette being apparently narrow and smooth. The 

 dentary bone (d.) is almost as deep as the premaxillse and does not 

 taper to the symphysis, where its inferior angle is bounded off, but 

 probably less so than is indicated in the side view of the imperfect 

 fossil. Its oral border must have been nearly straight, while its 

 lower margin, which is satisfactorily preserved, seems to trend 

 slightly downwards behind, where the bone becomes thinner. The 

 teeth are shown to be inserted in complete and distinct sockets, 

 with the inner wall as high as the outer wall, and neither cleft 

 nor pierced by nutritive foramina. The upper inner border of the 

 dentary bone itself, however, is much fractured and not well 

 exposed ; while the actual upper edge of the inner wall of the 

 tooth-sockets is formed by a small and loosely-apposed, laterally 

 compressed rod of bone (fig. 1 a, sph), which doubtless corresponds 

 with the curious anterior extension of the splenial described by 

 Marsh in Ceratosaurus^. The teeth of the mandible are com- 

 paratively small, none being larger than those of the premaxilla. 



1 O. 0. Marsb, "The Dinosaurs of North America" (16th Ann. Eep. U. S. 

 Geol. Surv. 1896), p. 159. 



