PROSOBRANCHIATA. 303 
laribus, equalibus: apertura oblongo-ovali ; labro fere recto ; sinu lato, mediocriter pro- 
Jundo, rotundato, ad humerum collocato. é 
Shell elongated, fusiform, concentrically furrowed; the spire nearly conical and 
moderately elevated, not quite equalling the aperture in length. The whorls, seven or 
eight without the pullus, are depressedly convex and are smooth and without ornament 
on the shoulders; the posterior margins, which slope very gently backwards, are 
traversed by a rather wide and deep concave furrow, and their sutural edge is simple ; 
the last whorl is girt round the shoulder by a narrow, riband-like band, scarcely 
elevated above the surface ; it is much contracted towards the front, and terminates 
in a wide and short, but distinct, canal, notched at the anterior extremity. The con- 
centric furrows are numerous, not very deep, even, and regular, and are separated by 
ridges of equal width with themselves, and rather depressed on the upper surface. 
The aperture is of an oblong-oval shape; the outer lip is very little arched, nearly 
straight, and situated on the shoulder; and the sinus is wide, moderately deep, and 
rounded at the extremity. 
This species is closely analogous with P. flecuosa (Miinst.), of which, perhaps, it 
may be considered a variety ; but the posterior margins are wider and more broadly 
furrowed, and the whorls do not present the curved costelle, nor are they bordered 
round the suture by the sharp, elevated line, found in that species. 
Size.—Axis, 9-12ths of an inch, nearly ; diameter, not quite 3-12ths of an inch. 
Localities.—Clarendon, Alum Bay (Stratum No. 4, Prestwich), and Potter’s Bar. 
No. 228. Pxrevrotoma variata. F. #. Edwards. Tab. XXXtI, fig. 11. 
P. testa elongata, angusta, sub-cylindricd, sub-turritd, longitudinaliter obsolete plicatd, 
transversim irregulariter sulcatd : spird elatd, bi-trientes totius teste fere equanti: anfrac- 
tibus convexiusculis ; marginibus posticis paullulo cavatis, ad suturam granoso-lineatis ; 
suleis transversis supra margines posticas et humeros angustis, confertis ; ceterum latioribus, 
distantioribus : apertura ob-ovali, in canali brevi, obliquo exeunte; labro valde arcuato ; 
sinu lato, profundo, ad humerum collocato. 
Shell long, narrow, somewhat turreted, and ornamented with obscure longitudinal 
plications, and irregular concentrical furrows: the spire is obtuse, sub-cylindrical, and 
much produced, being nearly double the length of the aperture. The whorls are depres- 
sedly convex ; the posterior margins, which slope gently backwards, are very slightly 
furrowed, and are bordered round the suture by a single row of very small granula- 
tions. The transverse furrows over the posterior margins and shoulders of the whorls 
are narrow, shallow, and irregular, those near the suture being more closely set than 
the others; over the middle and front parts of the whorls the furrows are broader and 
