BEACHES, ETC., OF THE SOUTH OF EN^GLAND. 299 



the shells and pebbles are embedded. At Portland I found 24 

 species,^ and to these Mr. A. Bell has since added 3 others, making 

 a total of 27 species. The richest locality is, however, the Thatcher 

 Rock, Torbay, where Mr. A. R. Hunt has made a collection of as 

 many as 43 species.^ There were 24 specimens in the collection 

 from Chilton Trinity formed by the late Mr. W. Baker, of Bridgwater, 

 whose names in the following list are altered in accordance with 

 recent synonyms. The collection is, I believe, lost. 



All the Portland shells are of littoral species, and almost all such 

 as are now living in the British area. Gwyn Jeffreys remarked 

 of them: — "The shells are rather northern than southern; but T 

 have not detected any pecuh'arly Arctic species, and certainly none 

 of a Mediterranean or Lusitanian type. All the species inhabit the 

 British coasts from Shetland to Yorkshire, except one, which I 

 consider undescribed, and propose to name Bissoa suheylindrata. 



Another species {Trochus Jielicinus) has not, so far 



as I am aware, been found south of Yorkshire and Dublin Bay. 

 The most northern known locality for another species (Trochus 

 umhilicatus) is Stornoway in the Outer Hebrides ; and it occurs 

 in a raised beach at Portrush." ^ 



The shells at the Thatcher Rock indicate, according to Mr. Hunt, 

 a greater range of depth, as well as a greater variety of sea-bottom. 

 He considers that many must have come from depths of 10 to 20 

 fathoms, and that while a large number are of species inhabiting 

 rocky coasts, there are others which now live only in sandy bays. 

 These shells are also, like those at Portland, of northern rather than 

 southern species. 



The Cyamium minutum is now rare in the South of England, but 

 common on the coasts of Scotland and Greenland ; the Nucula 

 nucleus, Tellina balthica, Lacuna puteolus, Littoynna rudis, Fu-ius 

 gracilis, Pleurotoma turricula, Pui'jpura lapillus, and Troplion 

 truncatum are also essentially northern species, but it is rather the 

 absence of southern forms than the presence of distinctly Arctic 

 forms that denotes colder waters — though there are no indications 

 of any extreme cold. It is a moUuscan fauna such as might now 

 exist on the shores of the North of Scotland or of Norway, as well 

 as on the South Coast of England, but not south of the English 

 Channel. 



Although the number of species is limited, it must be remembered 

 that we are dealing with a littoral fauna, and that we are ignorant 

 of the deep-water fauna of the Channel at that period. At the 

 present day, according to Mr. Damon, the number of species living 

 at all depths in the sea around Portland is not less than 281. 



The total number of the Raised Beach shells amounts to 64 

 species, forming a not inconsiderable proportion of the existing 

 littoral fauna. 



The Portland shells and the greater part of the Barnsta,ple Bay 



^ Quart. Journ. Geol. Soc. vol. xxxi. (1875) p. 33. 



2 Trans. Devon Assoc, vol. xx. (1888) p. 225. 



^ Quart. Journ. Geol. Soc. vol. xxxi. (1875) p. 52i 



