'\V{ 



f 



552 



iii;i'0UT — 1H84. 



and especially tbal of the Into Professor Stinipsunat Cliicapj. Tho kind- 

 nesa of ProCesHor »S)>eiK.'ci' Miiird enabled mo to witness the dredginj^s 

 wliicli were then carried on ulonfj the coast of Now England under tlio 

 charge of tho eminent und still living zoologist, Professor V'errill, of Yalo 

 College, 



Tho result of these examinations was coninuinieated by me to llie 

 IJritish Association at their Hrighton fleeting in the following year, undir 

 tho title of ' The Moilusca of lOurope compared with those of Kasteiii 

 North America.' I estimated llie former to consist of about 1,UOO species 

 (viz., 200 land and freshwater, and KOO marine), and tho latter to consist 

 of about 400 species (viz., llO land and freshwater, and 2'JO marine); 

 and I took !Mr. Pinney's edition of Professor Gould's 'Report on tlio 

 Invcrtebrata of ^Massachusetts,' published in 1S70, as tho standiird of 

 comparison for the American Moilusca. That work gave 401 spccie.s, of 

 which I consideretl 41 to be varieties iind tho young of other sjiecii's, 

 leaving 3G0 apparently distinct s[»ecie.-j. 1 reckoned that about 40 sjjeiios 

 might be added in cotisc({uence of tho later researches of Professor Verrill 

 and Mr. Wliitcaves on the coast of Js'evv England and in the (Julf of Si, 

 Jiawrence. I may hero observe, by way of parenthesis, that the relativti 

 number of sfiecies above mentioned has since been considerably increased, 

 both on the European and American (Continents, although tlio ])roportioii,s 

 may not be very dill'erent. I proceeded to identify 173 out of tho .'JGU 

 Massachusetts species as European — viz., land and freshwater ;}9 (out 

 of 110), and marine 184 (out of 250), the propc'tion in the former case 

 being 28 per cent., and in the latter nearly 54 cent. ; and 1 ])roduct'd 



a tabulated li.st in su])port of my statement. roposed to account for 



the distribution of the North American IMoLisca which 1 had tlius 

 identified by suggesting that the land and freshwater species might have 

 migrated from Europe to Canada through Northern Asia, and that most 

 of tho marine species nnght have been transported from the arctic sea.s by 

 the Davis Strait current southwards to Cape Cod, and the remainder from 

 the Mediterranean and eastern coasts of tlie Atlantic by the Equatorial or 

 some other current in a westerly direction. I renewed my objection to the 

 term ' representative species.' 



There were' some unavoidable errors in my list, because I had not 

 snflBcient means of making the necessary comparison of American and 

 European specimens on the spot, and some allowance must be conceded 

 for the well-known did'erence of opinion among naturalists with regard 

 to species and varieties; but 1 conscientiously believe that the above com- 

 parative analysis was not far iVom the mark. All tho marine species of 

 Moilusca enumerated in the list were "what may bo now termed inhabitants 

 of .shallow water, in contradistinction to tho deep-sea Moilusca which now 

 engage tho more special attention of conchologists. 



Since that time. Professor Whiteaves in Canada, and Professor Verrill 

 and Mr. Dall in the United States, have in an admiiablo and complttij 

 manner worked out and jjublished the Moilusca which have for many years 

 past been brought to light by means of tho deep-sea explorations made on 

 that side of tho North Atlantic. On the European side several equally im- 

 portant expeditions, with a similar object, have been also made during tlic 

 same period by the Jiritish, Norwegian, French, and Italian Governments; 

 and the Moilusca thus obtained have been published, or are in course of pub- 

 lication. My own papers in the ' Proceedings of tho Zoological Society of 

 London ' from 1878 to the present year, on the Moilusca of the Iiiijhinnvj 



