﻿PROSOBRANCHIATA. 



277 



No. 201. Pleurotoma mixta. F.E.Edwards. Tab. XXX, fig. 5, a, b. 



P. testa elongato-fusiformi, turitd. costellatd, concentrice sulcata simul atque omnino 

 ewilissime lineatd et cancettatd: spird elevatd, obtusd: anfractibm depresso-convexis, 

 obtuse angulatis, prioribus costatis, ceteris ad Jiumeros fasciold spirali cinctis ; postice 

 concavis, ad suturam marginatis ; ultimo anfractu coarctato, in cavalem longum, obliquum, 

 proditcto ; sulcis conccntricis latis, minime profundus ; lineis coneentricis elevatis, irregu- 

 laribus, lineis incrementi fortiter decussatis : aperturd oblongo-ovali ; labro arcuato, sub- 

 alceformi, ad humerum sinuato ; sinu latiusculo, prof undo, sub-lrigono. 



Shell lengthened, fusiform, turreted, ribbed, spirally furrowed, covered with 

 fine, concentric, undulating, raised lines, and cancellated ; the spire is rather 

 thick and elevated, exceeding the aperture in length. The whorls are bluntly 

 angulated at the shoulders, flatly convex at the sides, almost conical in front ; 

 the posterior margins concave, and slightly thickened and crenulated on the 

 sutural edges, where they present two rather distant concentric lines, more 

 elevated than the rest. The early whorls are obliquely costellated, but the 

 costellae become feeble and obscure on the penultimate whorl, and are altogether 

 lost on the last whorl, their place being supplied by a smooth, narrow, ribbon-like 

 band, which girds the whorls round the shoulders, and is defined by two prominent 

 lines and traversed along the middle by a third. The last whorl contracts gradually 

 towards the front, and terminates in a long, moderately wide, oblique canal, slightly 

 bent backwards at the extremity. The concentric furrows are wide, rather shallow 

 and rounded, and the concentric lines are numerous, irregular, thread-like, and 

 strongly decussated by the very prominent lines of growth. The aperture is of a 

 lengthened, oval shape ; the outer lip much arched, wing-shaped, projecting towards 

 the middle, and apparently smooth within ; and the sinus, which is placed on the 

 shoulder, is moderately wide, very deep, and nearly triangular in form. 



In the shape of the whorls, this Pleurotoma somewhat resembles P. conifer a ; it is, 

 however, a longer shell, and the mixed character of the ornamentation, different from 

 that of any other English Pleurotoma, entitles it to specific distinction. It is 

 apparently very rare. 



Size. — Axis, 1 inch and a half ; diameter, 5-12ths of an inch. 



Locality. — Barton. > 



