GASTEROPODA. 105 



This is an abundant species, and one I have not been able to identify with any- 

 known form. It approaches near to Turbo parvus, Mont. (p. 310), Cingula parva, 

 Flem. (p. 30 G), where that species is incorrectly stated to be without spiral stria?. 

 It appears to differ, however, in several particulars. Our shell has eleven or twelve 

 ribs on the body whorl, and is covered with spiral strias, or rather fine depressed 

 sulci, which are carried over the ribs, and upon the base ; it has a less elevated and 

 a less acuminated spire than B. parva, and has also denticulations within the outer 

 lip. Although abundant, the specimens of this species from the Crag are generally 

 rubbed or eroded, particularly at the ribs, where a portion of the shell has dis- 

 appeared, leaving a double ridge, with a depression between them. Occasionally, 

 the shell may be seen quite perfect, with the stride carried over the ribs ; whereas, 

 in my most perfect specimens of B. parva the striee are only visible between them. 

 Our shell more resembles B. rufilabris, Alder, but the upper whorls of that shell are 

 smooth, so also is the back of the body whorl, and our shell has a more orbicular 

 aperture. On account of these differences, it has been thought necessary to keep 

 them separated. The artist has given rather too many ribs on a volution. 



9. Rissoa obsoleta. 8. Wood. Tab. XI, fig. 11, a — b. 



Eissoa obsoleta. S. Wood. Catalogue 1842. 



B. Testa ovato-conicd, perforata crassd ; anfractlbus quinque, convexis, ventricosis, 

 transversim striatis. striis obsoletis ; suturis profimdis ; aperturd subrotundd ; labro extus 

 incrassato, marginato, intus dentato ; peristomate integro ; umbilieo parvo. 



Shell ovato-conical, ventricose, with a perforated base ; whorls five or six, convex 

 and tumid ; suture deep ; transversely striated ; striaa obsolete ; peristome con- 

 tinuous ; aperture subcircular, with a thickened and marginated outer lip ; and 

 about five or six obtuse teeth within the mouth. 



Axis, % of an inch ; diameter, f of the axis. 



Locality. Cor. Crag, Sutton. 



This is a very abundant species ; but I have met with it only from one locality, 

 and the specimens are all more or less rubbed or decorticated. The stria?, when 

 visible, are coarser, and most distinct upon the base of the shell ; and in a few 

 individuals they may be detected upon the upper volutions ; but in general the 

 shells are quite smooth. In its deep suture and inflated volutions it somewhat 

 resembles T. ventrosus, Mont. ; but it is a shorter species, and in its original con- 

 dition was covered with spiral strias. Many of my specimens are more tumid than 

 even the figure represents, and a large prominent and thickened varix is left upon 

 the outer lip. Somo specimens of this species have, no doubt, become smooth by 

 attrition ; but the obsolete character of the stria? has arisen, in all probability, from 

 a partial decomposition of the exterior. This may not be new, but I am not 

 acquainted with any species with which it can be identified. The only markings I 

 can perceive in any of my numerous specimens are the striee in a spiral direction. 



14 



