102 MOLLUSCA FROM THE CRAG. 



3. RISSOA SEMICOSTATA. Woodward. Tab. XI, fig. 10. 



TURBO SEMICOSTATUS (?). Mont. Test. Brit. p. 326, t. 21, fig. 5, 1803. 



Woodward. Geol. of Norf. t. 3, fig. 19, 1833. 

 RISSOA SEMICOSTATA. S. Wood. Catalogue 1842. 



Morris. Catal. Brit. Foss. p. 161, 1843. 



R. Testa brevi, ovato-comcd ; anfractibus quatuor vel quinque, convexis, tumidis ; 

 suturis profundis, longitudinaliter costulatis ; costulis nnmerosis, in ultimo anfractu 

 dimidiatis ; transversim striatis ; aperturd subrotundd ; labro intus dentato. 



Shell short, small, and conical, with four or five convex and tumid volutions ; 

 suture deep and distinct, longitudinally costated ; costse disappearing on the lower half 

 of the volution, transversely striated ; striae visible between the ribs and over the base ; 

 left lip slightly reflected over a small umbilicus ; outer lip thickened, and dentated 

 within. 



Axis, TO of an inch ; diameter, ^. 



Locality. Mam. Crag, Bramerton. ? Recent, British Seas. 



This is a rare shell in my cabinet, and Woodward speaks of it also as not being 

 abundant. It has about twenty ribs upon the last volution, and has an obtuse apex. It 

 is, I presume, the T. semicostatus of Woodward, as far as can be determined from his 

 indifferent figure, but probably not the T- semicostatus of Montague. I would suggest 

 the name of curticostata for this species, if it be really distinct. In my Crag specimens 

 the costse are visible upon the upper volutions. 



4. RISSOA VITREA. Mont. Tab. XI, fig, 3. 



TURBO VITREUS. Mont. Test. Brit. p. 321, t. 12, fig. 3, 1803. 



CINGULA VITREA. Flem. Brit. An. p. 308, 1828. 



RISSOA (?) VITREA. S. Wood. Catalogue 1842. 



CINGULA VITREA. Thorpe. Brit. Mar. Conch, p. 182, 1844. 



JR. Testa turritd, dongatd, subcylindraced, Icevissimd, politd, vitred, pettucidd, alba, 

 tenui fragili ; anfractibus 4 5, parum convexis ; suturis profundis ; apice obtusiusculo ; 

 aperturd ovatd ; labro simplici. 



Shell small, turriculate, subcylindrical, smooth, glossy, thin, white, and semitrans- 

 parent, with four slightly convex volutions ; suture distinct and deep ; apex rather 

 obtuse ; aperture ovate, contracted at the upper part ; peristome sharp, continuous ; 

 outer lip plain ; inner lip covering the umbilicus. 



Axis, \ of an inch. 



Locality. Cor. Crag, Sutton. Recent, British Seas. 



This elegant little fragile shell is at present rare, and appears perfectly identical 

 with the recent British species. It differs materially, in its vitreous texture, its glossy 

 and subhyaline appearance, from the general character of the shells of this genus, 

 which are usually opaque, and more or less externally ornamented. 



