﻿PROSOBRANCHIATA. 



255 



of that gentleman, the spire forms, in a 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. Pleurotoma verticillum. F. E. Edwards. Tab. XXIX, fig 3, a — c. 



P. testa turriculatd, longitudinaliter costettatd, omnino concentrice lineatd : spird 

 elatd, acuminata: anfractibus planulatis, ad humeros angulatis, antice coarctatis ; mar- 

 ginibus posticis depressis, sub-rectis, vix cavatis, obscure lineatis, ad suturam granidatis ; 

 ultimo anfractu in canali brevi terminanti ; costellis crebris, arcuatis, acutis, fere ad 

 basin tendentibus ; lineis concenlricis irregularibus, acutis, denticulatis : aperturd ovali ; 

 labro arcuato, acuto, intus plicato ; sinu prof undo, 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 



