PROSOBRANCHIATA. 201 
seven or eight, exclusive of the pullus, rounded at the shoulders, nearly straight on the 
sides, somewhat produced in front, and very slightly bent backwards. The concentric 
lines are equal, not very distant over the middle of the whorls, but varying in that 
respect in different individuals ; more crowded at the base and on the shoulders, distant 
on the posterior margins, which are much elevated, and pressed against the preceding 
whorls; occasionally on the last whorl of mature specimens additional faint lines 
appear. The spaces between the lines are very slightly concave, and finely crenu- 
lated by the lines of growth, which are very perspicuous over the whole surface of 
the shell. The aperture is narrow, straight, except at the base, where it is a little 
deflected, and scarcely emarginate ; the outer lip thin and sharp on the edge, very 
much thickened within, faintly crenulated on the inner margin by the concentric lines, 
of a roundedly elliptical shape, and detached from the suture by a wide but very 
shallow curvature. The anterior margin of the columellar lip is elevated and pro- 
longed in front, where it serves as the wall of the rudimentary anterior canal formed 
by the produced base of the shell. 
In specimens from Brockenhurst and Lyndhurst, the middle and upper parts of 
the whorls are perfectly smooth, with the exception of a single furrow which traverses 
the posterior margins; and the base of the shell presents numerous shallow furrows, 
which extend almost up to the middle of the whorl, instead of the sharp elevated lines 
which characterise the typical form. 
This well-known species, peculiar, I believe, to the Hampshire basin, forms the 
type of Mr. Swainson’s genus Cozordis. In the elevated conical spire, the almost 
semicircular form of the outer lip, and the produced base of the whorls, it presents 
the closest analogies with that section of the Pleurotomz formed of P. prisca, P. 
amphiconus, P. linearis, and similar species. Indeed, so closely does it approach to 
some of these, that, judging from external characters only, it is difficult to decide to 
which genus it should be referred. The straight, narrow aperture, however, is cer- 
tainly that of a cone, and indicates a necessity that the animal, in order that it might 
withdraw into the inner whorls, should be enabled to enlarge the space within the 
shell; a necessity which, as I have already stated, was met by the power of absorp- 
tion possessed by the animal. The curvature in the outer lip, also, is quite distinct 
in its character from the sinus in the outer lip of the Pleurotome. 
Size-—Type—Axis, | inch and 1-12; diameter, 5-12ths of an inch. Var.—Axis, 
1 inch and 3-12ths; diameter, 6-12ths of an inch. 
Localities—Barton, Alum Bay (No. 29, Prestwich), Lyndhurst, and Brockenhurst 
(New Forest). 
