ON RHAMPHORHYNCHUS BUCKLANDI 143 
Posteriorly, the rami of the mandible not only narrow to a depth 
of gths of an inch, but their planes gradually become vertical. The 
section of the ramus is a long oval, the width of which is not equal 
to more than a third of its length; and its bony substance is, here as 
elsewhere, extremely thin. 
There is not the slightest trace of an alveolus behind the fifth ; 
and the sutures which ordinarily mark out the components of a 
reptilian mandible are not visible on either the outer or the inner 
faces of the rami. 
The fang of a tooth is lodged in the third alveolus on the right 
side; and an entire tooth remains in the fifth alveolus of the same 
side. A similar tooth is much better displayed on the left side, 
implanted in the fifth socket, and directed upwards, forwards, and 
outwards. The total length of this tooth is about 14ths of an inch. 
Its exserted portion, or crown, is twice as long as the root, and is 
straight and flattened from side to side, tapering gradually to a sharp 
point. Where it leaves the alveolus, the tooth measures ;3,ths of an 
inch in diameter. The surface of the crown is smooth and devoid 
of ridges or folds,—the short, irregular, close-set, longitudinal strie 
with so much of the enamel-like outer layer as is preserved presents, 
seeming to be mere cracks. 
The extreme thinness of the bony walls of this mandible, the 
mode of implantation and the form of its teeth, clearly prove, as 
Lord Ducie had discerned, its Pterosaurian nature ; and the prolonged 
symphysial beak further dernonstrates its relations with that group 
of Pterosaurta called “Subulirostres” by Von Meyer, and thus 
described by that eminent paleontologist :— 
“The anterior end of the jaw passes into an edentulous point, on 
to which a horny beak was probably fitted; the eye had probably 
no osseous ring ;! the scapula and coracoid are anchylosed ;* and 
the tail is long and stout.”—Paleontographica, vol. i. p. 20. 
I am indebted to Mr. Rupert Jones for bringing under my notice 
two other Pterosaurian mandibles found in the Stonesfield slate itself. 
One of these, a very perfect and beautiful specimen, but unfortunately 
devoid of teeth, belongs to Professor Quekett, of the Royal College of 
Surgeons ; the other, consisting of a portion of a right ramus, forms a 
part of the collection of this Society. 
In the first of these specimens (Pl. XXIV. [Plate 10] fig. 2) the 
left ramus is completely exposed; and the fossil is so broken at 
about the junction of its anterior and middle thirds, as to display 
1 The characters marked * have been shown by subsequent investigations not to be 
constantly associated with the other peculiarities of Rhamphorhynchus. 
