146 ON RHAMPHORHYNCHUS BUCKLANDI 
The fossil in the Society’s Museum (Pl. XXIV. [Plate 1o] fig. 3) 
consists of a right ramus whose anterior end is broken off, the remain- 
ing part measuring 4 inches in length. The angle of the jaw is a little 
broken, and extends for hardly more than $th of an inch behind the 
posterior margin of the articular cavity. The latter is fully 4th of an 
inch long; and the coronary margin, in front of it, slopes upwards 
much more gradually than in the last-described specimen, so that 
the greatest vertical diameter of the mandible (0°65 inch) is 14 inch 
distant from the anterior edge of the articular cavity. 
From this point the upper margin of the mandible declines but 
very little towards the hindmost alveolus, where the depth of the 
ramus is 3ths of an inch. The hinder edge of this alveolus, which 
is oval and 1th of an inch long, is distant 2°35 inches from the 
anterior edge of the articular cavity. A second alveolus, of about 
the same size, is situated } an inch in front of the last; and a third, 
rather larger, is 4th of an inch in advance of the penultimate one. 
The inferior margin of the ramus is very slightly curved; and its 
vertical diameter, in front of the antepenultimate alveolus, is 0°55 
inch. The section here exposed is oval, and about 4th of an inch 
wide in the middle. 
The outer surface of the ramus exhibits very nearly the same 
sutural markings as in the preceding specimen. The “pit,” how- 
ever, is one inch in front of the anterior margin of the articular 
cavity. 
The two last-described specimens came under my notice only on 
the day on which I described the first to the Society; and I was 
then inclined to refer all three to one species; but having since been 
enabled to submit them to a much more careful examination, and to 
clear away so much of the matrix as obscured any doubtful points, 
I see many difficulties in the way of adopting that conclusion. 
Taking the most perfect of these fossils, or that belonging to 
Professor Quekett, as the type, I find, on a close comparison with 
the Sarsden specimen, that, although the proportions of the two, 
even down to the intervals of the teeth, are so similar that they 
might have belonged to individuals of very nearly the same size, 
there are many differences. The Sarsden mandible is altogether 
more robust; the planes of the rami, which are thicker, are more 
inclined outwards. The rostrum is not quite so deep in front of 
the first alveolus. The lower margin of the mandible is much less 
curved; and I can find no trace of the horizontal ridge or the 
vascular ramifications. I am not disposed to lay so much weight on 
