95 

 THE SHELLS OF THE HOLDERNESS 

 BASEMENT CLAYS. 



ALFRED BELL 



So much has been written about the basement clay, its origin 

 and contents, that another paper may be deemed superfluous 

 after the comprehensive memoirs and works of Professor 

 Phillips, and Messrs. Reid, Lamplugh, Drake and Sheppard 

 amongst others. 



A re-examination of the mollusca obtained from the Holder- 

 ness Clay now in the museums of London, Cambridge, York, 

 Hull, the private collection of Mr. Headley of Stamford, and 

 some material in my own possession, has enabled me to revise 

 and enlarge the published lists, with the kindly assistance of 

 F. W. Harmer, Esq., F.G.S., who is also adding to the number in 

 his memoir on the ' Pliocene Mollusca of Great Britain,' now 

 in course of publication by the Palaeontographical Society. 



The shells as at present listed represent two zones of life, 

 one dwelling between tide marks, and a deeper one reaching 

 thence to beyond 1,000 feet. The late Dr. Jeffreys proposed 

 to exclude most of those pertaining to the littoral zone, as not 

 coming from the clay itself but from a more recent bed. 



Some of the later gatherings have been taken at extreme 

 low tides, and the specimens obtained are not above suspicion. 

 Some that I have seen appear to be comparatively recent, or 

 perhaps from an overlying muddy clay of no great age. Their 

 number however is not great either in specimens or species ; 

 too few to interfere with the general result. 



Some of these species do occur at great depths. Mr. Friele 

 told Dr. Jeffreys that he had dredged Mytilus edulis and 

 Littorind rudis in 350 fathoms in company with Lima sub- 

 excavata. 



Of the 180 molluscs recorded below, at least 100 are no longer 

 living south of the Shetlands, and the remainder, with a few 

 doubtful exceptions, are all recorded by Sars and other writers 

 from Arctic Norway. Jeffreys described a few new species from 

 the Headley Collection but as since then, one (Rissoa wyville- 

 thomsoni) has been found alive at great depths (1,250 feet), 

 it is probable that the others, all small species, may be found 

 some day. 



Admete vividula Fabr. B. decussata inftata Posselt (PI. 



A. viridula conthouyi Jay. simplex Jeff. 11011 Midd.). 

 Amaura sulcosa Leche. B. dowsoni S. V. Wood. 

 Amauropsis islandica Gmel. B. elegans Moll. 



Astyris rosacea Gould. B, elegantior S. V. Wood. 



Bela angulosa G. O. Sars. B. exavata Moll. 



B. bicarinata Couth. B. harpularia Couth. 

 B. cinerea Moll. B. niulti striata Jeff. 

 B. decussata Couth. B. nobilis Moll. 



1917 Mar. 1. 



