PROSOBRANCHIATA. 255 
of that gentleman, the spire forms, ina majority of instances, very little more than half 
of the length of the shell, and the diameter, in some individuals, is relatively greater 
than that of the English shells. The tubercles are larger and coarser in the French 
shells, and the plication within the outer lip is found in them, although that character 
is not noticed by M. Deshayes. 
The chief distinctions between the English and French shells appear to lie in 
the more conical form of the whorls and the coarser tuberculation in the latter ; 
but these distinctions give very different aspects to the shells, and I have not 
ventured absolutely to refer the English shells to the French species, although they 
may perhaps be fairly regarded as forming a local variety. 
Size.—Axis, rather more than 5-12ths of an inch (11 millim.) ; diameter, rather 
more than 2-12ths of an inch (5 millim.). 
Localities.—Highcliff (where it is rather abundant) and Barton. 
No. 177. Pieurotoma verticittum. Ff. 2. Edwards. Tab. XXIX, fig 3, a—e. 
P. testd turriculatd, longitudinaliter costellatd, omnino concentrice lineatd: spiré 
elata, acuminata: anfractibus planulatis, ad humeros angulatis, antice coarctatis ; mar- 
ginibus posticis depressis, sub-rectis, vie cavatis, obscure lineatis, ad suturam granulatis ; 
ultimo anfractu in canali brevi terminanti ; costellis crebris, arcuatis, acutis, fere ad 
basin tendentibus ; lineis concentricis irregularibus, acutis, denticulatis: aperturd ovalt ; 
labro arcuato, acuto, intis plicato ; sinu profundo, sub-trigono, anticd in margine collocato. 
Var. testa costellis brevioribus, tuberculiformibus, ultimo anfractu obsoletis. 
Shell turriculate, longitudinally ribbed, concentrically lined : spire pointed, elevated, 
considerably exceeding the aperture in length ; whorls, eight or nine, flat-sided, slightly 
angulated at the shoulders, and much contracted in front; the posterior margins 
depressed, very slightly channeled, nearly straight, and most generally bordered round 
the sutural edge by a row of small tubercles. The longitudinal ribs are numerous, 
thin, sharp, and obliquely curved, and extend almost to the very front of the shell ; 
the concentric lines are elevated and sharp, and cover the whole surface of the shell ; 
over the margins of the whorls they are moderately close and regular; but over 
the middle and front parts of the whorls they become more elevated, more distant, 
and somewhat irregular, very fine lines occasionally intervening between the more 
prominent ones; these concentric lines strongly decussate the longitudinal ribs, 
rising into small, sharp tubercles at the points of decussation. The aperture is rather 
widely oval, and terminates anteriorly in a short, but distinct, canal; the outer 
lip is arched, and somewhat dilated in front; the inner lip narrow, but thick and 
prominent ; and the sinus, which is three-cornered in shape, deep, and wide, is placed 
in the front part of the margin. 
Occasionally specimens occur in which the longitudinal ribs are lost on the last 
