PROSOBRANCHIATA. 217 
No. 143, PLreuRotoma cocctpHora, F. 2, Edwards. Tab. XXVI, fig. 2. 
P. testa elongata, fusiformi, longitudinaliter costellaté, undique spiraliter granuloso- 
lineatis - anfractibus convexiusculis, angulatis, ad suturas incrassatis, granulatis ; margini- 
bus posticis mediocriter latis, vie cavatis, lineas filiformes confertas gerentibus ; costellis 
angustis ; lineis spiralibus numerosis, fortiter decussatis, inequalibus, lineis majoribus cum 
lineis tenuibus alternantibus : apertura ovali; labro leviter arcuato ; sinu fere semicirculari, 
in margine collocato. 
Shell elongate, fusiform, longitudinally ribbed, and having the whole surface orna- 
mented with spiral raised lines ; spire elevated, pointed : whorls (7—9) slightly convex, 
angulated ; the posterior margins moderately wide, nearly straight, and covered with 
fine, thread-like, concentric lines; two on the sutural edge are more prominent than 
the others, and decussated by the lines of growth so as to present a double row of 
fine granulations; the last whorl is produced in front into a long, and apparently 
nearly straight, and moderately wide canal; the costella are narrow, rather short, 
barely extending beyond the middle of the whorl, and are more or less distant in 
different specimens; the spiral lines over the middle and front parts of the shells are 
numerous and unequal, a slender, thread-like line occasionally intervening between 
others thicker and more prominent; all are deeply and regularly decussated by the 
lines of growth, so that the larger lines assume the appearance of rows of bead-like 
knobs. The aperture is of an oblong, oval shape; the outer lip slightly arched; and 
the sinus, which is placed towards the front of the margin, is wide, not very deep, 
and almost semicircular. 
This Pleurotoma closely resembles the young shell of P. crassa, of which, if it 
were not for the great difference in size, it might be considered to be only a local 
variety; the spire, however, is shorter and more conical, the whorls more angulated, 
less convex and more gradually attenuated in front; the posterior margins narrower 
and less concave; and the sinus nearer the shoulder, and rounder than in that 
species. The spiral lines also, broken into rows of beads by the lines of growth, 
form an ornamentation quite distinct in character from the broad, coarse bands which 
characterise P. crassa. 
The specimen figured forms part of Mr. Wetherell’s collection. 
Size.—Axis, rather more than 1 inch; diameter, 4-12ths of an inch. 
Locality—Highgate, where it is apparently very rare. 
