140 Ve sal, Ja DSy 
anteriorly by the olfactory duct, formed by the frontals above and 
the alisphenoids below. This duct has a diameter of three-eighths 
inch. Its length is unknown, as the anterior part is concealed in the 
matrix. It presents a marked contrast to the condition in modern 
crocodiles, in which its place is taken by a shallow trench and the 
alisphenoids are not continued forward and do not meet in the middle 
line. No other openings from the brain-case can be made out because 
of the presence of matrix where they might be expected to occur. 
Of the lower elements of the cranium the most anterior is the 
alisphenoid. This bone is of irregular outline, thin and curved in 
its front portion to encircle the olfactory lobes. Behind it sends 
outward and upward a strong process which rests in a depression in 
the under surface of the postfrontal and postorbital. To the rear 
the alisphenoid unites with the downward extension of the parietal 
above and with the proétic below, by oblique sutures. The lower 
margins of the alisphenoids gape in the posterior region and it is 
here that the neural foramina occur and that the epipterygoid is 
attached. As already indicated the anterior portion is concealed. 
Only the anterior part of the prodtic is exposed and this is seen 
to be united with the parietal above and the alisphenoid in front. ‘The 
lower anterior margin is free and borders the foramen ovale. Below 
this it unites with the pterygoid for a short distance and its lower 
posterior border meets the exoccipital. 
It seems probable that the basis phenoid occupies a relation similar 
to that in the crocodile, that its upper portion is covered by the ptery- 
goid and that the alisphenoid passes downward on the inner side of 
the pterygoid and epipterygoid to unite with the basisphenoid. 
In shape the basisphenoid is very irregular. Where it meets the 
basioccipital the two bones form a strong transverse ridge, of which 
however the basioccipital forms only a small part. Anteriorly it 
sends off the strong downward and forward-reaching basipterygoid 
processes. Between and above these a vertical rostral plate forms 
an incomplete septum called by Dr. W. J. Holland the presphenoid 
in Diplodocus. Posteriorly and superiorly the basisphenoid prob- 
ably unites with the posterior process of the pterygoid and with the 
exoccipital. 
The basiocci pital forms the chief part of the short stout occipital 
