y^? 
Marine Shells of Massachusetts. 273 
Last fall, I found this species in considerable num- 
bers, clinging to the wet sides-of the rocks, at and near 
low water mark. .In their station they resemble the 
Púrpura lapillus, but their habitat, unlike that of the P. 
lapillus, is confined to bays. This year I have not thus 
far (July) succeeded in finding them in this situation, 
but found a few near low water mark, upon a ind 
bottom.*. 
"This shell is fasid in Boston: harbor, but is not very 
common here. 
The operculum is tá lamellar, sibi 
broader above than below. 
CrnrTHIUM. 
C. ER Torren, oem Jour. Se: XXVIII, 352, 
Pasthi nigra, * — * * *« XXVI, 369. 
This species was first described by Col. Totten, from 3 
numerous immature specimens, and doubtfully referred 
to Lea's genus Pasithed. Not only the characters, but 
the immense numbers, of the young, which are often 
found without a solitary mature specimen, rendered 
them liable to be mistaken, on first acquaintance i 
the species, for the full grown shell. A very 
description, by the.same writer, from mature rime 
was afterwards published. ~ 
The mature shell differs from the young, not only in m 
the presence of a well marked canal, but i in the labrum, 
* During the a week, I have found numbers upon Em rocks imn 
= 
the harbors of of Dartmouth and Fairhaven, in the same situation as at .— 
a similar period of last year. 
VOL. III.—NO. II. 18 
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