Marine Shells of Massachusetts. 321 
. So as to lie almost wholly beneath the first of. the 
succeeding whorl; the suture consequently appears 
on the upper side of the first ridge, and is moderately 
impressed ; spaces between the ridges crossed by 
more or less elevated irregular lines, or coarse striæ 
of growth ; last whorl on the upper half, sculptured 
as the spiral whorls, with a fifth smaller revolving 
line on the lower part ; aperture ovate, one-eighth of 
the length of the shell, the line of its length making 
an angle of about 25° with the axis of the shell; Za- 
brum thin ; canal rather more than a third as Mos 
as the RES ot turning to the left. 
Length, .46 inch ; width, .13 inch. 
Cabinet of Bost. Bos Nat. Hist., of Middlebury 
College, of Mr, C. F. Shiverick, and my own. 
Station. In soft mud, below low water mark. 
Habitat. New Bedford and the vicinity. 
Remarks. This species was at first regarded as a 
variety of C. Emersonii, but the subsequent exami- 
nation of numerous specimens has satisfied me that 
the distinctive characters are constant. It differs 
from that shell in having a large elevated ridge in 
place of the carina on the upper part of the whorls, 
and in having three equal ridges in the upper whorls 
of the spire. "The entire want of granulations distin- 
guishes it from the common type of that species. It 
is distinguished from the Murer tubercularis of Mon- 
tagu by the same character. The latter is said to 
have but three revolving ridges, and is also of much 
less size than our shell. A number of dead speci- 
mens have been obtained by dredging, and Mr. Shiv- 
erick has found a few in a fresh condition. 
VOL. III. — NO. II. | 
