PROSOBRANCHIATA. 277 
No. 201. Preuroroma mixta. F. 2. Edwards. Tab. XXX, fig. 5, a, 6. 
P. testa elongato-fusiformi, turitd, costellata, concentrice sulcatd simul atque omnino 
exilissime lineaté et cancellatd: spird elevatd, obtusé: anfractibus depresso-convexis, 
obtuse angulatis, prioribus costatis, ceteris ad humeros fasciold spiral cinctis ; postice 
concavis, ad suturam marginatis ; ultimo anfractu coarctato, in canalem longum, obliquum, 
producto ; sulcis concentricis latis, minime profundis ; lineis concentricis elevatis, irregu- 
laribus, lineis incrementi fortiter decussatis : apertura oblongo-ovali ; labro arcuato, sub- 
dleformi, ad humerum sinuato ; sinu latiusculo, profundo, sub-trigono. 
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 
costelle 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. conifera ; 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, | inch and a half; diameter, 5-12ths of an inch. 
Locality —Barton. 
