PROCEEDINGS OF METROPOLITAN SOCIETIES. 293 



dentition of M. longirostris to English specimens of Mastodon teeth 

 in his possession, but pointed out a slight discrepancy in one respect, 

 and preferred to suspend his judgment for the present, as so little 

 was yet known respecting the crag animal. 



May 23rd. — Professor Sedgwick read the concluding portion of a 

 very elaborate paper, entitled " A Synopsis of the Series of English 

 Sandstone Rocks anterior to the Old Red Sandstone, and more par- 

 ticularly as developed in the counties of Devonshire and Cornwall." 

 He drew especial attention to the astonishing thickness of the beds, 

 and to the abundant existence of fossils, and of impressions of organic 

 remains, in certain metamorphic rocks of those counties, affirming 

 that the central granite is clearly of less high antiquity than several 

 of the superincumbent fossiliferous deposits. In the very animated 

 and interesting discussion which followed, Mr. Greenough, Mr. 

 Murchison, Professor Phillips, Mr. Lyell, Mr. Stokes, and others, 

 bore prominent parts ; and the eloquent and energetic final reply of 

 the eminent Cambridge professor, in reference to various remarks 

 and some allegations that his treatise was in great part devoid of 

 novelty, elicited the most flattering applause and admiration, and ri- 

 vetted the attention of the meeting to a late hour. Professor Sedg- 

 wick descanted at considerable length on the successive discoveries 

 which have been made in British Geology since the publication of 

 Mr. Greenough's excellent map, which he warmly eulogized; and 

 defended the claims of the contribution he had just brought forward 

 to contain much that was quite new to science, although it professed 

 chiefly to be a digest of our previous knowledge on the subject upon 

 which it treated. 



June 6th. — A paper by the Marquis of Northampton was first 

 read, in which were described several new species of minute multilo- 

 cular spiral shells, which his lordship had obtained in one or two lo- 

 calities from the chalk and its flints. Next a communication from J. 

 Taylor, Esq., was brought before the meeting, relative to the quick- 

 silver mines in Mexico, which were stated to be extremely rich, much 

 of the ore yielding forty per cent of metal. At present, however, 

 they were worked to great disadvantage, and not more than half that 

 quantity was extracted from the finest ore. Some native calomel had 

 been found in certain districts. A paper on the formation of obsi- 

 dian, or mineral glass, contributed by Mr. Edmonds, an officer of the 

 Kr.il del Monte Mining Company, was the next in order: it stated 

 that many layers of this substance, alternating with tracbytic sand- 

 lton«, had been observed, with evident indications of its having been 



