GASTEROPODA. 99 



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



Turbo ascaris. Tiirt. Conch. Diet. p. 217, No. CO, 1819. 

 TuRRiTELLA MINOR. Browii. 111. Brit. Concli. pi. 51, fig. 57-58, 1827. 

 Pykamis LiEvis. - - - pi. 50, fig. 51-52. 



TuRRiTELLA ASCARIS. Thorpe. Brit. Mar. Conch, p. xlv, fig. 21, 1844. 

 AcLis suPRA-xiTiDA. Lovhi. Ind. JIoU. Scand. p. 17, 1846. 

 Alvania scpra-nitida. S. Wood. Catalogue 1842. 

 — albella. Id. Catalogue, var. jS, fig. 1 1 c. 



A. Testa pusilld, turriculd, elonfjatd tenui ; apice ohtusiusailo ; anfractibus% — 9, con- 

 vewis, striafis, vel sulcatis ; sulcis circa quatuor, supra planatis; suturis profundis ; aperturd 

 ovafd, lahro incrassafo. 



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

 tions 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 sub- 

 circular, with a slightly curved and thickened outer lip ; base of volution plain, with 

 a slightly reflected left lip ; umbilicus small. 



Axis, i 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 volutions in all my specimens 

 are ^athout striae, 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 alhella 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 alhella in the handwriting of Dr. Leach, 

 they were found to correspond sufficiently to be considered identical, confiding 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. 



