THE 



VOYAGE OF H.M.S. CHALLENGER. 



ZOOLOGY. 



REPORT on the Scaphopoda and Gasteropoda collected by H.M.S. Chal- 

 lenger during the Years 1873-76. By the Reverend Robert Boog 

 Watson, B.A., F.R.S.E., F.L.S., F.G.S., &c, Ehrenmitglied cles 

 naturwlssenschaftlichen Vereins, Liineburg; Minister of the Free 

 Church of Scotland, Cardross. 



INTRODUCTION. 



The Scaphopods and Gasteropods of the Challenger Expedition form a fairly compact 

 group, including about 1300 recognisable species, new and old, with some 400 indis- 

 tinguishable forms. In many cases the specimens are few and poor. At twenty-eight 

 places not reckoned as dredging stations, but where gatherings were made on the shore, 

 in harbour, or in quite shallow water outside, 79 old species, 7 new, and 5 indistinguishable 

 forms were found, or 91 in all — on an average 3 from each. At seventy-five stations, 

 with depths varying from to 400 fathoms, 604 old species, 405 new species, and 341 

 indistinguishable forms were found, or 1350 in all, giving an average of 18 forms from 

 each. At forty-one stations, whose depths range from 400 fathoms down to 2650 (Station 

 325 — South* Atlantic— the greatest depth at which any specimens of the group were 

 obtained), there were found 89 old species, 135 new, and 46 indistinguishable forms, or 

 in all 270, being less than 7 forms from each. 



All persons interested in the Mollusca must feel some disappointment that these 

 groups are not, both in individuals and in species, better represented. The increasing 

 rarity of specimens in proportion to the depth of the station has been accepted as the 

 foundation of generalisations regarding the poverty of animal life in the great depths, 

 regarding the existence of zones of deadness, and regarding even the origination of 

 Molluscan life in shallow rather than in deep water, opinions which may indeed be true, 



(ZOOL. CHALL. EXP. — PART XLII. 1886.) Tt a 



