442 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 23,
making their appearance in groups of isolated peaks, projecting, as
it were, from a sea of alluvium. The author considered that this
alluvium could not have been produced by the action of the existing
rivers, and suggested that the Indus may formerly have flowed
into the sea by the Gulf of Cambay, the land at the same time being
much depressed below its present level. He indicated the evidence
in favour of this view furnished by various facts in the geology of
the district, and referred especially to the mode of occurrence of
laterite.
Discussion.
Sir P. Egerton mentioned that the Secretary of Mr. Burlinghame, the Chinese Ambassador, had informed him that the course of the Yellow River had, within a comparatively short period, changed its course by nearly 500 miles, and, by cutting off the supply of water to the Great Canal of China, had brought on the Taeping rebellion in consequence of the employment of the people being lost.
12. On a NEW ACCOUNT Saurian from the Lower Chalk. By James Wood Mason, Esq. F.G.S., &c. of Queen's College, Oxford.
(Plate XIX.)
While lately inspecting the rich and instructive collection of cretaceous fossils formed by my friend Mr. J. S. Gardner, F.G.S., my attention was arrested by what I at first sight took, judging from the precisely similar mode of implantation of the teeth, to be the anterior end of the snout of Mosasaurus, an extinct marine lizard closely resembling, as is well known, in many important structural characters, existing Monitors and Iguanas, and peculiar, as far as we at present know, to rocks of the Cretaceous period, both in Europe and America. But a closer examination of the teeth alone discovered differences from those of Mosasaurus altogether inconsistent with such an identification; the incorrectness of this becomes quite evident after the comparison which, thanks to the valuable researches of Dr. Leidy, it is possible to make of the fragment under consideration with the corresponding portion of the snout of Mosasaurus; it can further be seen from Dr. Leidy's* specimen that the structure of the fore part of the face of Mosasaurus differed in no essential particular from that of Monitor niloticus.
The fossil consists of the whole of the left praemaxilla† together with some portion of the contiguous maxilla; but, owing to the total obliteration of the maxillo-premaxillary suture, it is impossible to arrive at any satisfactory conclusion as to the extent of the former. The bone is so broken away posteriorly that no portion of the contour of the orbit is preserved, neither is the smallest guide furnished as to its position relatively to the aperture of the anterior nares. Its
- Cretaceous Reptiles of the United States, p. 39, pl. xix. fig. 6.
† It may be that the praemaxilla is absent.
