BALCH : LIST OF MARINE MOLLUSCA. 
153 
usually hidden, but rarely the progress of the animal is stopped, the 
foot, which before extended beyond the mantle border, retracted, 
and the extremely delicate and glassy gill-plates rapidly thrust in 
and out first on one side then on the other, at such times closely 
resembling the tips of some small beetles’ wings thrust from under 
the elytra. The form of the notaeum varies constantly in life, often 
appearing broadest posteriorly and sometimes slightly emarginate 
there but never so broad as long. 
The relation of this form to Verrill’s Doridella obscura , which it 
somewhat resembles superficially, is interesting but rather uncertain. 
Both Fischer and Bergh placed Doridella in the genus Corambe on 
the supposition that the anal notch had been overlooked and on the 
strength of the general likeness. But Verrill’s further description 
of the rhinophores as simple and without sheaths and of the gills as 
“tufted” and situated on the right (left?) side near the end would 
remove it not only from the genus Corambe but from the family of 
Corambidae. As the structure of Doridella is entirely unknown, 
placing it is only guess-w r ork, but if it proves to be a corambid 
form, as seems likely, the distribution of this family of six species 
will be curious, viz.: one species in the Sargasso Sea (Bergh, ’71), 
one in the Zuyder Zee (II. Fischer, ’91), one in the China Sea 
(Adams, ’58), one in the North Sea (Herbert, ’86), all these of one 
genus, and two in Long Island Sound occupying the same station 
and belonging to different genera. 
PITLMONATA. 
Bassomatophora. 
Auriculidae. 
Alexia my os otis (Drap.). Verrill (’73), p. 662. N. 
On stones at and above high-water mark. Usually near brackish 
water. Sometimes associated with Assiminea modesta. Uncom¬ 
mon. 
Melarnpus lineatus Say. M. bidentatus Verrill (’73), p. 662. 
M corneas Smith and Prime (’70), p. 399. S. 
Common on edges of salt marsh, on grass stems, etc. The 
banded variety occurs sparingly. 
