GASTEROPODA. 107 



Mont. (t. 12, f. 4). The volution of our shell is obtusely but distinctly angulated 

 on the upper part, giving the suture a deep depression. The specimens are gene- 

 rally more or less rubbed, causing the ribs to appear smooth ; but one individual 

 has distinct strise carried over the ribs. I am not acquainted with any recent 

 species with which it can be identified, and have therefore left it with its pro- 

 visional name. Small shells found in sand, even in a recent state, have their 

 characters sometimes obliterated, from friction by the agitation of the waters ; in 

 addition to which, many species from the Crag, particularly in this genus, have the 

 exterior altered by decomposition or decortication, which renders their identifica- 

 tion a matter of great difficulty. 



12. Rissoa supea-costata. S. Wood. Tab. XI, fig. 8. 



Rissoa supra-costata. S. Wood. Catalogue. 



B. Testa elongato-conicd, turritd ; apice parum obtuso ; anfractibus 5 — 6, convexis ; 

 superioribus costulatis, et transversim striatis ; anfractu ultimo Icevigato ; aperturd sub- 

 rotunda ; labro extus incrassato, intus denticulate ; labio vix reflexo ; umbilico parvo. 



Shell elongato-conical, turreted, thick, and strong, with a somewhat obtuse 

 apex ; volutions 5 — 6, convex, suture deep ; upper whorls longitudinally costated, 

 and transversely striated; last whorl smooth and tumid; aperture subcircular, 

 with a continuous peritreme ; outer lip thickened and reflected, with 4 — 6 den- 

 ticulations within ; and a small but distinct umbilicus. 



Axis, \ of an inch ; diameter, -§- the length of axis. 



Locality. Cor. Crag, Sutton. 



This is not a very abundant shell in my cabinet, and the specimens are rubbed, 

 their true character being thereby somewhat obscured. It bears a great resem- 

 blance to Pyramis similis (Brown's Illust. Brit. Conch, pi. 51, f. 20), which M. 

 Loven considers as a var. of membranacea, Adams, Helix labiosa, Mont. As it is at 

 present doubtful I have left it with its provisional name, although probably it may 

 be a known species. The upper whorls are furnished with 10 — 12 rounded and 

 vertical costse, while the lower one is smooth and naked, and it has not the slightest 

 vestige of a thickening or fold upon the columella. Rissoa nana, Grat. (Foss. de 

 Bord.), has the upper volutions costated, but has no umbilicus. 



The names of several of the species in this genus are given as new, while pro- 

 bably they are not so ; being, however, unable to identify them with any known 

 forms, they are left for the present with the provisional names given to them in my 

 Catalogue. 



