Geological Society of London. 43 



in so long a time, very thick masses have accumulated in many 

 places. He explained some methods of distinguishing gravels 

 according to their origin. 



Turning to the subject of Caves, he thought they should be care- 

 ful not to confound (III. i.) the question of the age and origin of the 

 caves themselves with (III. ii.) that of the deposits in the caves. 

 He then described some of the more important caves of the district, 

 explaining the evidence upon which he founded the opinion that 

 the deposits in Pontnewydd Cave were postglacial palEeolithic. He 

 arrived at the same conclusion with regard to the deposits in the 

 Ffynnon Beuno Caves. Combating the objections to this view which 

 had recently been urged, he pointed out that the drifts associated 

 with the deposits in those caves cannot have ben formed before the 

 submergence described under II. (ii. ), because they contained north- 

 country fragments and flints, and that, even if they were of the age 

 of the submergence, they would not be preglacial ; that they cannot 

 have been formed during the submergence, as the sea would have 

 washed away the bones, etc., from the mouth of the cave, and its 

 contents must have shown some evidence of having been sorted by 

 the sea. He considered that the greater part of the matei-ial that 

 blocked the upper entrance of the upper cave belonged to the 

 surface-drifts described under II. (iii.), and were, as they stood, 

 almost all subaerial. 



He further pointed out that, so far as palaeontologists had been 

 able to lay before them any chr-onological divisions founded on the 

 mammalia, the fauna of the Ffynnon Bueno Caves agreed with the 

 later rather than with the earlier Pleistocene groups. 



II._December 1, 1886.— Prof. J. W. Judd, F.R.S., President, in 

 the Chair. — The following communications were read : — 



1. "On a new Genus of Madreporaria — Glyphastrcea, with re- 

 marks on the Olyphastrcea Forhesi, Edw. & H., sp., from the Tertiaries 

 of Maryland, U.S." By Prof. P. Martin Duncan, M.B., F.R.S., 

 F.G.S., etc. 



The specimens of Septastrcea Forhesi, Edw. & H., were examined 

 many years ago, and the author had always a doubt about their generic 

 position. Lately a very well-preserved specimen has been received, 

 which when compared with those in the jS^ational Collection and care- 

 fully studied, is found to have a columella and a remurkable dome of 

 endotheca at the top of the base of the calicular fossa, resembling the 

 well-known structure in Clisiophxjllum. 



Two opposite primary septa become very narrow, extend inwards, 

 form, with another structure, a narrow linear columella, and tiius 

 produce the appearance of a continuous lamella. The other primaries 

 and some of the secondary septa reach this long structure, and the 

 endotheca stretches between the ends of the septa, their sides, and the 

 columella, and closes up the interseptal loculi. The epithecal dis- 

 sepiments are dome-shaped at the base of the calice, and are ornamented 

 with sparsely distributed granules : superficially a corresponding 

 granulation occurs on the narrow and also on the wide marginal parts 

 of the septa. 



