PROSOBRANCHIATA. 283 
No. 208. Prevroroma simiuuima. F. EB. Edwards. Tab. XXX, fig. 4, a—c. 
P. testé elongato-fusiformi, sub-turritd, costellatd, omnino spiraliter lineata: spird 
elata, acuminata: anfractibus convexiusculis, ad humeros obtuse angulatis ; postice concavis, 
marginatis ; costellis numerosis, angustis, sub-rectis ; lineis spiralibus confertis, filiformibus, 
erreguaribus: aperturd ovali, in canali longo exeunti; labro arcuato; sinu lato, medio- 
criter profundo, sub-trigono, ad humerum collocato. 
Var. crasstinga ; testd anfractibus acute angulatis, tribus vel quatuor lineis supra 
medias partes cinctis. 
A long, narrow, fusiform shell, ribbed and covered with elevated spiral lines : spire 
sub-turreted, pointed, equalling the aperture in length; whorls, seven or eight 
exclusive of the pullus, slightly convex, bluntly angulated at the shoulders, hollowed 
round the posterior margins and thickened at the sutural edges, which are bordered 
by one or two prominent raised lines. The ribs are numerous, narrow, nearly 
straight, short, not extending beyond the middle of the whorls, and becoming obsolete 
on the last whorl of the mature shell; the spiral lines are closely set, fine, thread-like 
and regular over the margins and shoulders of the whorls, but over the middle 
these lines alternate with others still more slender. The aperture is oval and 
produced in front into a long, narrowish, and nearly straight canal ; the outer lip is 
arched, and presents at the posterior part on the shoulder of the whorl, a very wide 
and moderately deep sinus, triangular in shape. 
In the variety noticed, the whorls are more sharply angulated, and they present 
over the middle, three or four coarse, elevated lines, with an occasional intervening 
slender line ; but in other respects the shells agree with the typical form. 
In the general aspect the present species closely resembles P. Prestwichii ; but it 
may be distinguished from it by the turreted spire, the depressed concave posterior 
margins and the less convex sides of the whorls, and especially by the character of the 
longitudinal ribs, which are more numerous, straighter, and narrower, and do not 
extend backwards beyond the shoulders ; whereas the coarse, obliquely curved ribs in 
P. Prestwichii reach up to the very suture; and the transverse lineation is also of a 
finer character. From P. Wetherellii, to which it also approaches, the present 
species is separated by the more slender form, the more vertical ribs, and the 
narrower posterior margins of the whorls. 
Size.—Axis, rather more than 1 inch; diameter, 4-12ths of an inch. 
Localities.—Highgate, Potter’s Bar, Hampstead, Muswell Hill, Southampton, 
Alum Bay (Stratum No. 4, Prestwich), and Clarendon, at which latter place it is 
common. ‘The variety occurs at Highgate, Potter’s Bar, and Southampton. 
