BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. I49 
species are to be found. And six of them are comprised in the list of predominantly 
northern species given below. 
Interesting comparisons between the distributions of different members of the 
same genus may be made for the genera Anomia, Arca, Astarte, and Pecten. ‘The case 
of the two local species of A starte is peculiar inasmuch as there is nothing in their ranges, 
so far as we know, which gives a clue to the differences which they display in their 
local distribution. 
Certain species among the Jamellibranchs dredged by us have never been taken in 
a living condition. Of these the most striking examples are Arca ponderosa and Thracia 
convadi. The former, indeed, has never been recorded living, so far as we know, north 
of Cape Hatteras, although fairly fresh shells have sometimes been found. It seems 
likely that both of these species may bury themselves too deeply in the bottom to be 
taken by the dredge. 
Those species which were taken at 10 or more dredging stations have, as usual, 
been grouped, so far as possible, into predominantly northern and predominantly 
southern forms. The ranges given for the Pelecypoda and for the mollusks in general 
are those stated by Dall. 
Predominantly northern (13). 
Anomia aculeata (chart 124)....Arctic Ocean to Cape Fear. 
Pecten magelianicus (chart 125). Labrador to Cape Hatteras. 
Mytilus edulis (chart 127)...... Arctic Sea to North Carolina. 
Modiolus modiolus (chart 128). . Arctic Sea to North Carolina (Florida ?). 
Modiolaria nigra (chart 129). .... Arctic Sea to Cape Hatteras. 
Crenella glandula (chart 130)...Arctic Sea to Cape Hatteras. 
Nucula proxima (var. trunculus 
Dail) (chart 134). $0005 i chccsew Nova Scotia to New York. 
Yoldia limatula (chart 135).....Arctic Ocean to North Carolina. 
Venericardia borealis (chart 137) Hudson Strait to off Hatteras. 
Cardium pinnulatum (chart 142) Labrador to Cape Lookout. 
Cyclas islandica (chart 144)....Arctic Ocean to Cape Hatteras (at latter point in deep water only). 
Spisula solidissima (chart 153). . Labrador to Cape Hatteras. 
Thracia conradi (chart 155)..... Labrador to Cape Hatteras. 
Predominantly southern (1Q). 
Ostrea virginica (chart 122)... . Prince Edward Island to West Indies. 
Anomia simplex (chart 123)... .Cape Sable to Martinique. 
Pecten gibbus borealis (chart 
Bee ak 2) Aa ltiath Seo sis ds asd) Nova Scotia to Tampa, Fla. 
Arca ponderosa (chart 131)..... Provincetown to Yucatan. 
Arca transversa (chart 132).....Cape Cod to Mexico. 
Arca campechiensis pexata 
Kelatt THe ids ae belt 203s. Cape Cod to Texas. 
Crassinella mactracea (chart 
BAO da bivinsl oie aoc eae ols + Cape Cod to Florida. 
Divaricella quadrisulcata(chart 
BAM ste Barn v'n.0 ee Oty MA ER Cape Hatteras to Brazil. (Woods Hole region.) 
Levicardium mortoni(chart 143) Nova Scotia to Venezuela. 
Venus mercenaria (chart 145)...Nova Scotia to Yucatan. 
LLL SAS 
@ Dr. Dall has kindly furnished us with some unpublished notes, which modify to some degree the ranges as stated in his 
‘Preliminary Catalogue of the Shell-bearing Marine Mollusks.”’ 
