144 ON RHAMPHORHYNCHUS BUCKLANDI 
in transverse section, not only this ramus, but its fellow of the 
opposite side. 
The left ramus is 43 inches long. The posterior portion of its 
inferior edge is nearly straight ; but it becomes curved anteriorly, so 
as to have a slight downward concavity. Beneath the two anterior 
alveoli the concave curvature sweeps into a somewhat decided con- 
vexity ; and in front of a line drawn through the anterior alveolus, 
the lower contour of the mandible is prolonged forwards and upwards 
into the inferior margin of the rostrum, in which the extremity of the 
mandible ends. 
The superior edge is, for the most part, slightly convex upwards, 
but anteriorly it exhibits a slight concavity, while posteriorly, or near 
the articular end, it suddenly curves downwards and backwards. It 
is rendered slightly sinuous by the projection of the margin of the 
alveoli. 
The angle of the jaw is formed by a thin and short process, 
rounded off posteriorly, which projects for about 3th of an inch 
behind the posterior edge of the articular cavity, and has about the 
same depth, if measured along a perpendicular line drawn immediately 
behind that edge. 
The articular cavity itself is about 3th of an inch long. It is. 
concave upwards; and its anterior margin is so much higher than 
the posterior, that a line joining the two, slopes gradually upwards. 
into the convexity of the coronary region. The cavity is somewhat 
broader than it is long; and its anterior and posterior boundaries. 
converge internally, so that it has the form of a triangle with its 
base turned outwards. The posterior boundary passes into the thin 
angular process, the anterior into the still thinner coronary part of 
the jaw. This part attains its greatest elevation about °7 inch 
from the angle of the jaw, the depth of the mandible being at this 
point *4 inch. 
There are altogether seven alveoli, the hindmost of which is an 
inch and a half distant from the angle of the jaw. This alveolus 
measures rather more than ¢th of an inch in length; the others 
are about 3th of an inch long, or a little more; the second and 
third are largest; and all are oval. The posterior edge of the 
sixth alveolus (counting from before backwards) is 1°9 inch from 
the angle of the jaw; of the fifth, 2°3 inches; of the fourth, 2:8 
inches ; of the third, 3:1 inches; of the second, 3:5 inches; of the 
first, 3°8 inches. When the rostral end of the mandible was entire, 
the whole length of the ramus was probably very little under five 
inches, as the rostrum must have extended fully 6 inch beyond the 
