104 Frof. 0. C. Marsh — A New American Jurassic Dinosaur. 



the symphysis. The articular, angular, and subangular bones are well 

 developed, but the coronary and splenial appear to be small. 



The Teeth. — The dentition of Biplodocus is the weakest seen in any 

 of the known Ditiosauria, and strongly suggests the probability that 

 some of the more specialized members of this great group were 

 edentulous. The teeth are entirely confined to the front of the jaws 

 (Figures 1 and 2), and those in use were inserted in such shallow 

 sockets that they were readily detached. Specimens in the Yale 

 Museum show that entire series of upper or lower teeth could be 

 separated from the bones supporting them without losing their relative 

 position. Figure 5 shows a number of detached teeth. The series of 

 teeth was found with the remains of Stegosaurus, and hence was 

 at first referred to that genus, as was also the specimen represented in 

 figure 3 of the same plate. ^ The teeth of Stegosaurus are now known 

 to be of a different type, somewhat resembling those of Scelidosaurus. 

 Fig. 5. Fig. 6. 



_ Fig. 5.— Maxillary teeth of B. longus, side 

 Tiew, one-half natural size ; e, enamel ; 

 r, root. 



Fig. 6. — Section of maxillary of B. longus, 

 one-half natural size, showing functional tooth 

 (fourth) in position, and five successional teeth 

 and dental cavity ; a, outer wall ; h, inner 

 wall ; c, cavity ; /,'foramen. 



The teeth of Biplodocus are cylindrical in form, and quite slender. 

 The crowns are more or less compressed transversely, and are covered 

 with thin enamel, irregularly striated. The fangs are long and 

 slender, and the pulp cavity is continued nearly or quite to the crown. 

 In the type specimen of Biplodocus, there are four teeth in each 

 premaxillary, the largest of the series ; nine in each maxillary ; and 

 ten in each dentary of the lower jaws. There are no palatine teeth. 



* See Silliman's American Journal of Science, vol. xix. p. 255, March, 1880. 



