442 PROCEEDINGS OP 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 exist- 

 ing 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. Egeeton mentioned that the Secretary of Mr. Burlinghame, 

 the Chinese Ambassador, had informed him that the course of the 

 Yellow Eiver 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 AcEODONT Saurian /rom 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 cre- 

 taceous fossils formed by my friend Mr. J. S. Gardner, P.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 Eu- 

 rope 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 consi- 

 deration with the corresponding portion of the snout of Mosasaurus ; 

 it can further be seen from Dr. Leidy 's* specimen that the struc- 

 ture of the fore part of the face of Mosasaurus differed in no essen- 

 tial particular from that of Monitor niloticus. 



The fossil consists of the whole of the left prsemaxilla f 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 con- 

 tour 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 Beptiles of the United States, p. 39, pi. xix. fig. 6. 

 t It may be that the prsemaxilla is absent. 



