374 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



then its surface would be agitated. I have cleaned out your shells 

 and I find that in nearly all of them there was a marly matrix still 

 remaining, not the material that one would find in a swamp or morass, 

 hut in a lake with a chara vegetation. A lake, moreover, to deposit 

 such material must be of some depth, say 12 feet at least. Were it less 

 than that marl would not form, it would be a carbonaceous mud. 

 Since so many of the L. pereger are decidedly not normal there must 

 have been abnormal conditions tliere. This raises the question in my 

 mind whether the new Limnseas maj^ not after all only be auricular ia, 

 which owing to unfavourable conditions were stunted during the 

 latter period of their life, and so unable to properly develop the last 

 whorl. I still think that these are the same as the Irish shells, a new 

 form, but I have stated the alternative." 



These remarks agree with the observed conditions, for the lacustrine 

 area consists of a deposit of a marly nature, of a thicUness of 2 or 

 3 inches, on the top of blown sand about 30 inches thick, the fresh- 

 water shells occurring only in the upper 2 or 3 inches. 



The lacustrine area of the Gear Sands is confined to the eastern side 

 of the highest sand dunes. I could find no extension of it towards 

 the Penhale Sands. Probably the underlying rocks render that 

 impossible. At Penhale Sands there is a swampy area at a much 

 lower level than the lacustrine area aforesaid, surrounded by lofty 

 sand dunes. I should think the lower level here is not more than 

 80 or 90 feet O.D., compared Avith 200 feet for the lacustrine area. 

 Above the swampy part, which, however, was dry when I was there 

 in Januarj' last, and on the north of it, there are three terraces, 

 apparently natural. On the upper terrace I found a valve of Pecten 

 varius, bored by Cliona perforans, and on the two lower terraces valves 

 and broken fragments of Mytilus edidis were abundant. I also found 

 a fragment of another bivalve and a few Patella vulgata and a Purpura 

 lapillus. The broken Mytilus edulis, etc., may be the debris of 

 a kitchen midden, but some at least may have reached their present 

 position by being rolled up the slopes of sand by the wild Atlantic 

 gales, seeing that the slope to the seashore is in some places continuous 

 from the beach upward and the blown sand completely masks the 

 cliffs, if indeed they exist at these particular spots. In the swampy 

 sand at about 125 feet O.D. a very few Limnma pereger occurred. 



In conclusion I have to thank my friend Mr. A. Santer Kennard for 

 the kind trouble which he has taken to work out the puzzling lacustrine 

 specimens. 



