1869.] Geology and Falseontology. 295 



(2.) Messrs. J. W. Salter and Henry Hicks contribute descrip- 

 tions of five new species of Trilobites, from the " Menevian Group," 

 St. David's, belonging to the genera Gonoiori/phe and Paradoxides, 

 illustrated by two 8vo plates. 



(3.) Mr. Alfred Tylor, F.Gf.S., describes the Quaternary 

 Gravels of the Aire Valley at Bingley, of the 1 aff Vale, of the 

 Valley of the Khonda, the Cave-section (called Bacon Hole) 

 Gower, and the sections at Crayford, Erith, and Salisbury, and 

 he compares the angles of deposition of Gravel-beds concealing the 

 escarpment of the Chalk in these last three localities with the escarp- 

 ment at Brighton and Sangatte. 



The bulk and height of the Quaternary deposits had strength- 

 ened the conviction which he expressed in his paper on the Amiens 

 Gravel,* (1) That there was a long period, reaching nearly to the 

 Historical ejwch, in which the rainfall was excessive, and which he 

 termed the " Pluvial Period." 



(2) That the ice-action (of which there is evidence) was subor- 

 dinate to the aqueous action. 



(3) That the fossiliferous Quaternary deposits have been best 

 preserved where they have been formed in cavities lying between 

 the edge of the bank of a river, estuary, or sea, and an escarpment 

 running parallel with it at no great distance. 



(4) That the immediate source of the gravels was the high 

 lands adjoining the rivers, whence they had been washed down by 

 rain, with the assistance of lateral streams, into the lower ground, 

 where they had come in contact with larger quantities of running 

 water, had been mixed with rolled materials, and spread in thick 

 beds over the bottoms and slopes of valleys or the sides of escarp- 

 ments. 



(5) The escarpment is usually concealed under a coating of 

 gi-avel or loess. 



Mr. Tylor argues that with a rainfall such as we now have it 

 would be impossible that such widely-extended gravel-beds could be 

 spread over an extensive area, and reach to a height more than 

 150 feet above the level of the Thames. It is equally impossible, 

 he thinks, for the present volume of the Thames to have j^i'oduced 

 fluviatile beds at all equivalent in size to those of the ancient 

 Thames. 



That the condition of the beds, which rise above the 50-feet 

 level, points rather to pluvial than to fluvial action. 



Mr. Tylor informs us there are no traces of marine remains in 

 the Thames-valley gravels. Assuming that they are of marine 

 origin, gravel-banks are not the safe depositories of organic remains. 

 A walk along the Chesil Bank, or the Shingle-bcach at Weybourn 



* See 'Quart. Joum. Gool. S()(\,' vol. x\iv.. ISCR, p. 103. 



X 2 



