PROSOBRANCHIATA. 301 
No. 225. Pxreuroroma insienis. F. 2. Edwards. Tab. XXXII, fig. 14, a, 3b. 
P. testé sub-turritd, transversim denticulato-lineata : anfractibus depresso-convexiusculis, 
ad humeros angulatis, tuberculatis ; marginibus posticis canaliculatis, ad suturam fasciolé 
per-elevata, fastigui-formi, cinctis ; ultimo anfractu, antice costellato, in canalem breviusculum 
producto ; tuberculis numerosis, pliciformibus, obliquis ; lineis concentricis supra margines 
posticas et humeros exilibus, regularibus; supra medium ultimi anfractis distantibus, 
elevatis, scabratis: aperturd ovali ; labro arcuato, ad humerum sinuato ; sinu lato, trian- 
gulart. 
A somewhat broad, turreted shell, ornamented with concentric, raised lines; the 
spire, which consists of five or six volutions, is pointed and moderately elevated, 
forming about half the length of the whole shell. The whorls are angulated at the 
shoulders, and armed with a series of closely set, narrow, laterally compressed, oblique 
tubercles ; the posterior margins are deeply channeled and are girt near the suture by 
a much-elevated, ridge-like band, which is granulated in the earlier whorls; the last 
whorl is depressedly convex on the sides, much contracted towards the front, and 
terminates in a narrow and rather short canal. The concentric lines over the poste- 
rior margins and immediately in front of the shoulder, are slender and rather closely 
set, distinct, and regular: on the middle of the last whorl appear four or five regular, 
concentric, raised lines; of these, the one nearest the shoulder is granulated and 
separated from that next in front by a very narrow, concave furrow ; the raised line, 
second from the shoulder, is transversely denticulated, and in front of this appear 
two other almost equally prominent and moderately distant lines, which are also denti- 
culated; the intermediate spaces are nearly flat, and are traversed along the middle by 
very fine and scarcely perceptible raised lines, also denticulated. Three or four much 
elevated sharp, or faintly granulated, concentric lines traverse the canal. The bases of 
the denticulations on the posterior median line, are prolonged into rather broad, 
flat, longitudinal ribs, which extend to the origin of the canal. The aperture is oval ; 
the outer lip arched and indented at the shoulder by a very wide, moderately deep, 
sub-trigonal sinus. 
This species presents some analogy with P. denticula ; but the shell is broader, the 
spire shorter, the tubercles on the shoulder narrow and fold-like, the sinus much 
wider, and the sculpture different in character. It is apparently very rare. 
Size—Axis, rather more than 4-12ths of an inch; diameter, 2-12ths of an inch. 
Locality.—Alum Bay (Strat. No. 4, Prestw.) 
