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), Cinyula parva, 

 Flem. (p. 306), where that species is incorrectly stated to be without spiral strise. It 

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

 on the body whorl, and is covered with spiral striae, 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 ft. 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 disappeared, 

 leaving a double ridge, with a depression between them. Occasionally, the shell may 

 be seen quite perfect, with the striae carried over the ribs ; whereas, in my most 

 perfect specimens of R. parva the striae are only visible between them. Our shell more 

 resembles R. rujilabris, 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. 



RISSOA OBSOLETA. S. Wood. Catalogue 1842. 



R. Testa ovato-conicd, perforate!, erased; anfractibus guinque, converts, ventricosis, 

 transversim striatis, striis obsoletis ; suturis profundis ; aperturd subrotundd ; labro extus 

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



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

 and tumid ; suture deep; transversely striated ; striae obsolete ; peristome continuous ; 

 aperture subcircular, with a thickened and marginated 'outer lip ; and about five or six 

 obtuse teeth within the mouth. 



Axis, \ of an inch ; diameter, 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 striae, 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 quit 

 smooth. In its deep suture and inflated volutions it somewhat resembles T. ventrosus, 

 Mont.; but it is a shorter species, and in its original condition was covered with spiral 

 striae. 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. Some specimens of this 

 species have, no doubt, become smooth by attrition ; but the obsolete character of the 

 striae 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 striae in a spiral direction. 



14 



