164 O. C. Marsh—New Family of Dinosaurs. 
Immediately in. front of this cavity, the pterygoids begin to 
expand, and soon form a broad, flat plate, which stands 
along its inferior border with the vomer. A little in front of © 
the middle, 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 semi-oval bone fitting into the concave 
anterior border of the pterygoid, and sending forward a slen- 
der 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 process of the premaxillary. Along its upper 
and inner border, it unites with the pterygoid, except at the 
end, where 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 
once from the Adlantosauride, which have a wide pituitary 
canal connecting the brain cavity with the throat. In the 
Morosauride, the pituitary fossa is quite small. ; ae 
he posterior portion of the brain of Déplodocus was dimin 
tive. The hemispheres were short and wide (Plate IV, figure 
1), and more elevated than, the optic region. The olfactory — 
lobes were well developed, and separated in front by a vertic® 
osseous septum. The very close proximity of the external 8 
nasal opening is a new feature in Dinosaurs, and appears 10: ne 
be peculiar to the Sauropoda. © 
Tur LOWER JAWS. 
The lower jaws of Diplodocus are more slender than in 20Y 
of the other Sawropoda. The dentary especially lacks the 
massive character seen in Morosaurus, and is much less robust 
than the corresponding bone in Brontosaurus. The short dete 5 
tigerous portion in front is decurved (Plate ILI, figure 1), and 
