﻿PROSOBRANCHIATA. 



301 



No. 225. Pleurotoma insignis. F. E. Edwards. Tab. XXXII, fig. 14, a, b. 



P. testa sub-turritd, transversini denticulato-lineatd : anfractibus depresso-convexiuscidis, 

 ad humeros angulatis, tuberculatis ; marginibus posticis canaliculars, ad suturam fasciold 

 per-elevatd,fastigii-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 anfractus distantibus, 

 elevatis, scabratis : aperturd ovali ; labro arcuato, ad humerum sinuato ; sinu lato, trian- 

 gulari. 



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-l2ths of an inch. 



Locality Alum Bay (Strat. No. 4, Prestw.) 



