1919. Bell. — Fossil Shells from Wexford and Manxland. 113 



If " concentrated " from the chocolate-coloured clay, 

 this should contain a similar group of forms, which it 

 does not, or if it does, the evidence has never yet been 

 published, and the Pliocene species are referred by Messrs. 

 Cole and Hallissy to the gravels. 



The Blackwater cliffs extend nearly continuously for 

 twelve miles along the coast, with a thickness of 70 feet, 

 rising at the Head to 160 feet, made up of marls, sands and 

 gravels alternately disposed, with many small shell- 

 fragments in the latter (Kinahan). Calcreted sands abound 

 here and in the Isle of Man. Their age being problematical 

 and their origin equally so, I may be excused the suggestion 

 that they are the relics of an early Irish sea or inlet 

 which originally started in early Pliocene times from 

 North Cornwall, and lasted till the tectonic changes, of 

 which we get such abundant evidence in Eastern 

 England, permitted the influx of northern waters, northern 

 shells, and floating ice-floes with their rock debris. Northern 

 shells began to arrive in England in the Upper or Boytonian 

 stage of the Coralline Crag, but the Northern Tellen (T. 

 halthica) did not appear till the very latest stage of the 

 Norfolk Icenian at Weybourn, and the presence of this shell 

 in the Wexford-Manx sea would impty that it was at this 

 stage the northern barrier was broken down in this direction. 



I would suggest further that the shelly gravels at 

 Blackwater and other Wexford localities (and their sporadic 

 occurrence is in favour of this conclusion) are current-swept 

 sandbanks such as are recorded by Wyville Thomson off 

 the Portuguese coast^ where one haul of the dredge brought 

 up 113 species of shells alone. Of these 40 per cent, were 

 new to science, numerous Sicilian Tertiary forms and others 

 of northern types, besides many living Lusitanian species. 



The Turbot Bank, off the coast of Antrim, may be referred 

 to as another example of shelly sands and gravels. From 

 here and the immediate neighbourhood 246 species of 

 shells have been procured, mostly dead. It is doubtful 

 if any of these are in situ, certainly not such forms as Acirsa 

 borealis, Natica affinis, Trochus cinerarius, Trophon clath- 

 ratus, Astyris rosacea, Buccinum cyaneum, or Molleria 



1 " The Depths of the Sea," p. 183. 1879. 



