400 E. T. NEWTON ON A CKOCODIL1AN JAW FROM
seventh tooth, it is tolerably certain that it did not extend beyond the tenth or eleventh tooth. The splenial elements, however, may have formed part of the symphysis, and carried it a little farther back.
At present I am nnable to refer this jaw to any known genns ; and this not because of the imperfection of the specimen, but rather because the peculiar characters which it possesses are not to be found, so far as I am aware, in either of the genera hitherto described. The lenticular area and the oblique grooves by which this is separated from the rest of the median area do not appear to be represented in either of the genera mentioned by M. Deslong- champs *, and certainly they are not shown in any of his figures. Metriorhynchus, it is true, has four large teeth in the front of the lower jaw ; and supposing that the anterior tooth in our specimen was a small one, then there would be four large teeth here also ; but then they do not occupy the same relative positions, for in Metriorhynchus it is the first to the fourth teeth which are large, while in our specimen it would be the second to the fifth. It is quite possible that the anterior tooth in this specimen was large also. The depth of the lateral grooves, especially towards the front, and the presence of the oblique grooves are likewise very marked characters, and the relative proportions of the jaw seem to be equally peculiar.
The specimen forming the subject of this communication I obtained from a mass of rock which had fallen from one of the uppermost beds of the Corallian Rocks west of Sandsfoot Castle, Weymouth, at the point where the road ends upon the shore. The rock itself is a greenish-brown, sandy grit, and appears to belong to the bed 3 of Messrs. Blake and Hudleston's section of the Sandsfoot- Castle Beds f .
In the same block were also found two shells, which my esteemed colleague Mr. Etheridge agrees with me in referring to Goniomya liter ata and Pinna lanceolata.
DESCRIPTION OF PLATE XVI.
(Figs. 1-4 one half natural size.) Fig. 1. Crocodilian lower jaw from the Corallian of Weymouth; seen from below, the upper surface being imbedded in the matrix and the lower portions denuded so as to expose the alveoli. Fig. 2. Same specimen, front part seen from above. Fig. 3. Transverse section at a in fig. 2. Fig. 4. Ditto at b in ditto.
Fig. 5. Crown of young tooth preserved in the third alveolus of the left ramus ; view of outer surface. 5a. Side view of apex of same tooth.
5b. Transverse section of ditto a short distance from apex. Fig. 6. Tooth restored from several portions.
- Notes Paleontologiques, vol. i.
t Quart. Journ. Geol. Soc. vol. xxxiii. p. 270.
