PROSOBRANCHIATA. 267 
except in the young state, and the nearly straight margins of the whorls instead 
of the deeply furrowed margins which characterise that species. 
Size.—Axis, 4-12ths of an inch; diameter, 1-8th of an inch. 
Locality.— Alum Bay (No. 29, Prestwich); rare. 
No. 189. Preuroroma turpis. Ff. 2. Edwards. Tab. XXVIII, fig. 2, a—e. 
P. testa elongata, fusiform, spiraliter sulcatd, in juventd costellatd: spird productd, 
bitrientes totius teste in longitudine fere equanti: anfractibus convexiusculis ; ad humeros 
angulatis ; postice declivis, late cavatis, ad suluram crenulatis; ultimo anfractu antice 
sensim attenuato, in canali perbrevi terminato; sulcis spiralibus crebris, undulatis, 
obscuris: apertura oblongo-ovali ; labro arcuato, acuto; sinu sub-triangulari, lato, medio- 
criter profundo, in margine collocato. 
Shell long, fusiform, spirally sulcated, and, in the young state, longitudinally 
ribbed ; the spire much produced, forming nearly two third parts of the whole shell ; 
whorls, seven or eight, slightly convex, angulated at the shoulders; the posterior 
margins slope gently backwards, are plicated round the sutural edge, and are deeply 
channeled, imparting somewhat of a turreted character to the spire; the body-whorl 
tapers towards the front with so gradual a contraction as to be almost conical. In the 
young shell the whorls present rather numerous, nearly straight ribs, which are lost 
about the fourth or fifth whorl. The spiral furrows are shallow, close-set, slightly 
undulating, obscure, and frequently decussated by the lines of growth. The aperture 
is a lengthened, ovate form, and terminates in front in a short, wide, indistinct canal ; 
the outer lip is arched, thin, sharp-edged, and smooth within; and the sinus is three- 
cornered in shape, not very deep, and wide, extending across the whole width of the 
margin. 
This Pleurotoma presents a general resemblance to P. pyrgota; the latter species, 
however, may be easily distinguished by the finely crenulated and more sharply 
angulated shoulders of the whorls and the prominent, ridge-like line which borders 
the suture. 
Size.—Axis, rather more than 1] inch; diameter, 1-3d of an inch. 
Localities.—Clarendon, Southampton. 
No. 190. Prevroroma susuta. F. £. Edwards. Tab. XXIX, fig. 13, a, 6. 
P. testa subulatd, spiraliter obsolete lineatd, fere levi: spird elaté, sub-conicd : 
anfractibus antice planiusculis, postice cavatis, ad suturam sub-incrassatis, marginatis ; 
