No. 7.— List of Marine Mollusca of Coldspring Harbor , Long 
Lsland, with descriptions of one neic Genus and t\co new Spe¬ 
cies of Nudibranchs. 
By Francis Noyes Balch, Cambridge, Mass. 
With one plate. 
Tiie following list of Mollusca — representing eight weeks’ 
work during August and September, 1898, and September, 1899, 
at the Biological laboratory of the Brooklyn institute of arts and 
sciences at Coldspring Harbor, Long Island, under the direction 
of Dr. C. B. Davenport — claims no especial extent, complete¬ 
ness, or novelty. It is put on record as a contribution toward more 
exact knowledge of local distribution and variation and because the 
nature of the locality gives it a certain interest. It represents a 
fairly distinct facies of molluscan life—the fauna of the oyster 
beds, broadly speaking. From this point of view its homogeneity 
and the absence of stragglers lend it value. Probably almost every 
species enumerated lives on the spot where found or in the imme¬ 
diate vicinity. This characteristic makes it a good sample of 
actual conditions of life in that interesting transition region where 
the “Virginian” and “Acadian” (or “Boreal”) faunas overlap. 
From this point of view it is, so far from being homogeneous, 
strikingly heterogeneous. 
Coldspring Harbor (Davenport, ’98) is an indentation some 
five miles long and one mile wide opening into Long Island Sound 
some forty miles east of New York. It is shoal (for the most 
part less than two fathoms), land-locked, tranquil, warm, muddy, 
and subject to a constant inflow of detritus and fresh-water from 
the high moraine hills surrounding it and abounding in streams. 
The shores are little varied. Commonly, a narrow strip of salt 
marsh leads to mud Hats, to eel-grass beds, to oyster beds ; or the 
steep “slides” of the carved moraine run down to a narrow beach 
of loose sand and stones thinly strewn with glacial boulders which 
shelves gently to the mud flats again. Genuine sand beaches are 
wanting, sandy bottom is rare, though sand often underlies the silt 
at the depth of a few feet. Rocky habitats other than the smooth 
and inhospitable boulders are few, though piles, sea walls, and old 
