﻿PROSOBRANCHIATA. 



251 



and thence tapers gradually towards the front, so as to form a wide and short, but 

 distinct, canal ; the aperture is of a compressed-oval shape ; and the sinus, which is 

 placed in the marginal furrow, is wide, shallow, and triangular in form. 



The general resemblance between the present species and P. turgidula might 

 suggest the propriety of uniting the two ; but, on a careful examination, differences 

 will be found which seem to justify their separation. Thus, in the present species, 

 the spire is more obtuse ; the whorls more contracted in front ; the posterior margins 

 deeply furrowed and bordered at the suture by a broad, thick band ; the longitudinal 

 ribs are more numerous, more decided in character, and less oblique ; and the sinus 

 is shallower and more pointed. 



A specimen in my cabinet, obtained from the Artesian well at Southampton, has 

 the surface of the shell spirally furrowed instead of banded, and the anterior canal 

 a little shorter and wider. These differences, however, do not appear to be 

 sufficiently important for specific distinction, and I have therefore regarded the shell 

 in question as a variety of the present species. 



Size. — Axis, 6-12ths of an inch ; diameter, rather more than 2-12ths of an inch. 



Localities. — Highgate, Southampton. 



No. 172. Pleurotoma turgidula. F. E. Edwards. Tab. XXIX, fig. 4, a — c. 



P. testa fusiformi, sub-turritd, spiraliter sulcata, costellatd : anfractibus sub-ventricosis, 

 ad humeros angulatis, postice declivis vix cavatis, ad suturas unicd serie granularum 

 instructis ; sulcis spiralibus irregular ibus, minime prof undis, fere obsoletis ; costellis obliquts, 

 angustis : aperturd ovali, antice in canali breviusculo exeunti ; labro arcuato ; sinu sub- 

 trigono, latiusculo, media in margine collocato. 



Shell fusiform, sub-turreted, concentrically furrowed, and longitudinally ribbed ; 

 the spire, formed of six volutions exclusive of the pullus, is moderately elevated, 

 forming rather less than half of the shell : the whorls are roundedly convex, almost 

 ventricose, and bluntly angulated at the shoulders; the posterior margins, which 

 slope gently backwards, are nearly straight, and the sutural edge is girt by a single 

 row of small, round tubercles. The concentric furrows are numerous, irregular, 

 and almost obsolete over the posterior margins and middle of the whorls, but 

 a little deeper and more perspicuous over the front ; the longitudinal ribs are 

 rather numerous, narrow, oblique, and very short, barely extending to the middle 

 of the whorl, and slightly swelled at the posterior extremities ; on the last whorl 

 the ribs become reduced to small and not very prominent tubercles. The aperture 

 is oval, and terminates in front in a short, but distinct and moderately wide, canal ; 

 the outer lip is slightly arched ; the sinus, placed in the very middle of the posterior 

 margin, is wide, rather shallow, and somewhat triangular in form. 



