654 PLIOCENE MOLLUSCA. 



Distribution, — Recent : British coasts, abundant. West Atlantic, Mediter- 

 ranean, Adriatic. Norwegian coast — Finmark and Lofoten Islands to the 

 Christiania fiord. Circumpolar — Spitsbergen, White Sea, Iceland, Massachusetts, 

 Beh ring Strait, Vancouver Island. 



Fossil : Iceland Crag. Butleyan : Btttley, Hollesley. Icenian : 

 Norwich zone — Bramerton, Thorpe, Postwick, Brundall, Horstead, Beccles, Yarn 

 Hill, Ditchingham, Dunwich, Aldeburgh. Weybourne zone — Belaugh, North 

 Walsham, Bacton, Mundesley, East Runton, Weybourne. Isle of Man. Wexford. 

 Pleistocene : Billockby, Speeton. Kelsey Hill, Bridlington, March, Nar Valley, 

 Portland, Selsey, and other localities in Great Britain and Ireland. Uddevalla, 

 Littorina Sea, Christiania fiord — Cyprina beds to Tapes-banks (Brogger), Trond- 

 hjem (0yen). 



Remarks. — It is with many apologies to my good friend M. Dautzenberg that 

 T retain the specific name of rudis for the present shell rather than saxatilis, Olivi, 

 recently adopted by himself and the late Dr. Kobelt. L. rudis seems to me such 

 a well-established specific name, having been widely and generally in use for more 

 than a hundred years, that I fear the suggested alteration might lead to consider- 

 able confusion among English geologists. 1 



Forbes and Hartley expressed the opinion in 185:] (,,y>. cit., vol. iii, p. 43) that 

 Olivi did not define his L. su,i'<ttilis with sufficient clearness to secure its positive 

 identification and that the latter may have been L. neritoides. In the meantime 

 Maton's older specific name rudis (1797) has been adopted by Jeffreys and 

 generally in other scientific works, including the list published by the Concho- 

 logical Society of Great Britain in 1902. 1 



The L. rudis of English waters with its varieties is fairly abundant in the 

 Icenian deposits, especially at Bramerton near Norwich, where we seem to be 

 approaching the shore line of the Crag sea of that period. Specimens of it differ 

 considerably in size, form, colour and sculpture, some of them being here given 

 under the varietal names adopted by Jeffreys and other authorities. In colour 

 most of them are of a light yellowish-grey, while a few are deeply ferruginous. 

 In size they vary from the minute var. saxatilis of Olivi to the large and solid 

 var. globosa. Most of the recognised varieties of this species have now been 

 found at Bramerton or Thorpe near Norwich. 



As a recent shell L. rudis is distinctly littoral, occurring on beaches within 

 the reach of the tide, or in some cases above high-water mark. It has a wide 

 range in the eastern hemisphere, mainly northern, but it is also reported from 

 the eastern and western coasts of North America. M. Gignoux considers that 

 the typical L. rudis has not at any period penetrated into the Mediterranean 

 (op. cit., p. 557). 



1 The L. rudis of the Crag is a different shell from that for whirl. I have adopted the varietal nam,. 

 saxatilis. 



