466 A. FE. Verrill— Catalogue of Marine Mollusca. 
canal; on the penultimate whorl there are usually four, rarely five, 
spiral lines visible, below the carina. The nuclear whorls are small 
and prominent; the apex is small and soon two strong spiral lines 
appear; the uppermost of these becomes a carina, on the whorl next 
to the nucleus, while above and below it thin transverse riblets 
appear; the normal sculpture then commences. But the upper whorls 
are usually badly eroded. The aperture is oblong-ovate, angulated 
posteriorly at the shoulder, narrowed at the base of the canal, which 
is somewhat elongated and contracted; sinus shallow, broadly con- 
cave; outer lip thin, strongly flattened, below the shoulder in the 
middle, and ineurved at the base of the canal. Columella nearly 
straight in the middle, a little excurved or sigmoid, anteriorly. 
Color white, or greenish white, epidermis pale green, thin, glossy. 
The uncini are remarkably broad and short, lanceolate, acute, with 
the edges involute, not distinctly barbed; basal process short, broad. 
An ordinary example measures in length, 14"™"; breadth, 675 ; 
length of body-whorl in front, 9°25; its diameter, 55; length of 
aperture, 7; its breadth, 2°5"", Specimens ascertained to be males, 
by dissection, agree in proportions with these measurements. 
This species is one of the most common in Massachusetts Bay, 
Cape Cod Bay, and the Gulf of Maine, im 15 to 115 fathoms. Off 
Cape Cod (sta. 304), 122 fathoms. It is most frequent in 25 to 60 
fathoms, and occurs both on muddy and on gravelly and shelly bot- 
toms. It was also taken by the U. 8. Fish Commission in Casco Bay, 
in 17 to 30 fathoms, in 1873; Halifax harbor and Bedford Basin, in 
16 to 41 fathoms, 1877. I have seen no specimens from farther north. 
This shell has, undoubtedly, been generally confounded, under the 
name of “ B. turricula,’ with several other related species. It closely 
resembles some forms of B. scalaris and of B. exarata, but differs 
greatly from both in its dentition. From both, the shell can usually 
be distinguished by the absence of spiral Imes on the subsutural 
band, and by having fewer and more distant spiral lines on the mid- 
dle of the whorls. 8B. exarata has decidedly more numerous and 
smaller ribs with smaller nodules, and also a shorter canal and differ- 
ently shaped aperture. B. scalaris has nearly the same form of aper- 
ture and canal; but it is a stouter shell, with the whorls less flat- 
tened, and the aperture is broader. 
With eroded specimens, such as often occur, it will not always be 
possible to distinguish these three species with certainty, without 
examining the odontophore. It is not possible, at present, for me to 
identify this shell positively with any of those described by G. O. 
