[ 69 ] 

 IX. Proceedings of Leaimed Societies. 



GEOLOGICAL SOCIETY. 



[Continued from vol. xxii. p. 226.] 



November 3, 1886.— Prof. J. W. Judd, F.R.S., President, 

 in tbe Chair. 



THE following communications were read : — 

 1. " On tbe Skull and Dentition of a Triassic Saurian, Galesaurus 

 planiceps, Ow." By Sir Eicbard Owen, K.C.B., F.R.S., F.G.S., &e. 



2. " Tbe Cetacea of tbe Suffolk Crag." By R. Lydekker, Esq., 

 B.A., F.G.S., &c. 



3. " On a Jaw of Hyotherium from tbe Pliocene of India." By 

 R. Lydekker, Esq., B.A., F.G.S., &c. 



November 17.— Prof. J. W. Judd, F.R.S., President, in tbe Chair. 



The following communication was read : — 



" On the Drifts of the Yale of Clwyd, and their relation to the 

 Caves and Cave-deposits." By Prof. T. M c Kenny Hughes, M.A., 

 F.G.S. 



The Author divided his subject as follows : — I. Introductory Re- 

 marks ; II. The Drifts, viz. (i.) The Arenig Drift, (ii.) The St.-Asaph 

 Drift, (iii.) The Surface-Drifts; III. The Caves, viz. (i.) The Caves 

 themselves, (ii.) The Cave-Deposits ; IV. Conclusion. 



He exhibited a table showing the tentative classification he pro- 

 posed. II. (i.) The Arenig Drift, he said, might be called tbe 

 Western Drift, as all the material of which it was composed came 

 from the mountains of Wales ; or the Great Ice-Drift, as it was tbe 

 only drift in the Vale which contained evidence of direct ice-action. 

 He traced its course from the Arenig and Snowdon ranges by striae 

 on the solid rock and by tbe included fragments, a large proportion 

 of which were glaciated. There are no shells in this drift. 



II. (ii.) The St.-Asaph Drift might, he said, be called the Northern 

 Drift, as it was tbe deposit in which fragments of north-country 

 rocks first appeared ; or tbe Marine Drift, as it was, excepting the 

 recent deposits at the mouth of the estuary, the only drift in the 

 Yale which showed by its character and contents that it was a sea- 

 deposit. It contained north- country granites, flints, and sea- shells, 

 of which he gave lists. Most of them are common on the adjoin- 

 ing coast at the present day, a few are more northern forms. 

 None of the rocks are striated, except those derived from the 

 Arenig Drift (i.). 



II. (iii.) The Surface-Drifts included the older and newer alluvia 

 of the rivers, the Morfa Rbuddlau Beds or estuarine silt, the recent 

 shore-deposits or Rhyl Beds, and all the various kinds of deposits 

 known as talus, trail, rain-wash, head, run-of-tbe-bill, &c., of which, 

 in so ]ong a time, very thick masses have accumulated in many 

 places. He explained some methods of distinguishing gravels accord- 

 ing to their origin. 



Turning to the subject of Caves, be thought they should be careful 



