GASTEROPODA. 99 



1. Alvania ascaris. Turt. Tab. XII, fig. 11, a — c. 



Turbo ascaris. Turt. Conch. Diet. p. 217, No. GO, 1819. 

 Turritella MiNou. Brown. 111. Brit. Conch, pi. 51, fig. 57-58, 1827. 

 Pyramis l/evis. - - - pi. 50, fig. 51-52. 



Turritella ascaris. Thorpe. Brit. Mar. Conch, p. xlv, fig. 21, 1844. 

 Aclis supra-nitjda. Lovhi. Ind. Moll. Seand. p. 1/, 1846. 

 Alvania supra-nitida. <S. Wood. Catalogue 1842. 

 — ALBELLA. Id. Catalogue, var. j6, fig. 1 1 c. 



A. Testa pusilld t fttrriculd, elongatd fenui ; apice obtusit/sculo ; anfractibus 8 — 9, con- 

 vexis, stria tis, vet sulcatis ; sulcis circa quatuor, supra planatis ; suturis jjroftindis ; aperturd 

 ovatd, labro incrassato. 



Shell minute and slender, with an elevated spire, and slightly obtuse apex ; 

 volutions 8 — 9, convex, with three or four large, transverse, elevated, and rounded 

 ridges upon each whorl ; upper part plain and smooth ; suture deep ; aperture 

 ovate, or subcircular, with a slightly curved and thickened outer lip ; base of 

 volution plain, with a slightly reflected left lip ; umbilicus small. 



Axis, j of an inch. 



Locality. Cor. Crag, Sutton. Recent, Coast of Ireland and North Seas. 



About twenty specimens of this pretty little shell are in my cabinet, and as the 

 upper volutions are smooth and glossy, and the upper part of the whorl is free 

 from striae, I considered it distinct from ascaris ; for, in Dr. Turton's description, 

 as well as in Brown's figure, the striae are represented as regular and equidistant, 

 and my dependence for comparison was upon their descriptions. Mr. Alder, 

 however, has informed me that it is the same species as Turbo ascaris, Turt., and I 

 have restored that name upon his authority. The first two or three of the volu- 

 tions in all my specimens are without strias, but that is probably from erosion. 

 The apex of this shell is reversed and papilliform, and the external ridges are 

 sometimes visible within the mouth, from the thinness of the shell, and two or 

 three specimens have a slightly thickened varix on the outer lip. Two of my 

 specimens have a diameter equal to nearly half the axis, while in others it is not 

 more than a quarter. The dimensions of the aperture .vary in length from a 

 quarter to- one third the length of its axis. 



Alvania albella of my Catalogue is probably only an eroded form of this species. 

 In comparing the Crag shells in the first instance with a specimen upon a tablet 

 in the British Museum, having the name of Alvania albella in the handwriting of 

 Dr. Leach, they were found to correspond sufficiently to be considered identical, con- 

 fiding in the recent specimen as a perfect shell. As this was intended by Dr. Leach 

 for the type of his genus, the name was used as such in my Catalogue, and continued 

 here for the same reason. The introduction of numerous incorrect forms by Risso 

 is not sufficient to invalidate the right of Dr. Leach to the above name. 



