The Skeleton 67 
The basioccipital (14) is seen projecting caudad 
as tHe single occipital condyle; it will be described 
in connection with the posterior aspect of the skull. 
The jugal (5), quadratojugal (12), and quadrate 
(8) may all be seen from this view. The first two 
have been sufficiently described in connection with 
the dorsal aspect; the last will be further described 
in connection with the lateral aspect. 
Just caudad to the posterior nares is a small 
opening, the unpaired Eustachian canal (eu). 
The Lateral Aspect (Fig. 21). As will be seen by 
the figure, practically all of the bones visible in this 
view have already been described, except those of 
the mandible, which will be described separately. 
At the base of the skull are, however, two bones, 
the basi- and alisphenoid, that have not been 
described and that show as well in this as in any 
other view. The basisphenoid (just below v and 
hidden by the pterygoid) was mentioned in connec- 
tion with the quadrate, with whose posterior mar- 
gin it articulates. It is an unpaired bone of very 
irregular shape. Anteriorly it is flattened out to 
form the rostrum, a rectangular process that forms 
the posterior part of the interorbital septum; in 
fact it is the only part of the septum present in 
a prepared skull, since the rest is cartilaginous. 
Dorso-laterally the basisphenoid articulates with 
the alisphenoid; posteriorly with the basioccipital; 
ventrally with the pterygoid; and posteriorly with 
the exoccipital and basioccipital. On the dorsal 
