178 



DINOSAURS OF NORTH AMERICA. 



a process extends downward and outward, for union with the transverse 

 bone. In front of this process, uniting with it and with the transverse 

 bone, is the palatine. 



The palatine is a small semioval bone fitting into the concave ante- 

 rior border of the pterygoid, and sending forward a slender process for 

 union with the small palatine process of the maxillary. 



The vomer is a slender, triangular bone, united in front by its base to 

 a stout process of the maxillary, which underlaps the ascending proc- 

 ess of the premaxillary. Along its upper and inner border it unites 

 with the pterygoid, except at the end, wbere for a short distance it 

 joins a slender process from the palatine. Its lower border is wholly 

 free. 



THE BRAIN. 



The brain of Diplodocus was very small, as in all dinosaurs from the 

 Jurassic. It differed from the brain of the other members of the 

 Sauropoda, and from that of all other known reptiles, in its position, 

 which was not parallel with the longer axis of the skull, as is usually 

 the case, but inclined to it, the front being much elevated, as in the 

 ruminant mammals (PI. LXXVI, fig. 4). Another peculiar feature of 



Fig. 28 — Dentary boue of Diplodocus longua; seen from the left. 

 a. edentulous border; *■. symphysis. 



One-third natural size. 



the brain of Diplodocus was its very large pituitary body, inclosed in a 

 capacious fossa below the main brain case. Tbis character separates 

 Diplodocus at once from the Atlaiitosaurkhc, which have a wide 

 pituitary canal connecting the brain cavity with the throat. In tbe 

 Morosaurida' the pituitary fossa is quite small. 



The posterior portion of the brain of Diplodocus. was diminutive. 

 The hemispheres were short and wide and more elevated than the 

 optic region. Tbe olfactory lobes were well developed, and separated 

 in front by a vertical osseous septum. Tbe very close proximity of the 

 external nasal opening is a new feature in dinosaurs, and appears to be 

 peculiar to the Sauropoda. 



THE LOWER JAWS. 



The lower jaws of Diplodocus are more slender than in any of the 

 other Sauropoda. The dentary especially lacks the massive character 

 seen in Morosaurus, and is much less robust than the corresponding 



