530 TROCHIDiE. 



almost beaded near the undulations. There are five rather 

 narrow whorls, which rapidly enlarge from a fine and 

 rather acute apex ; they are peculiarly well-defined, each 

 base being suddenly perpendicular whilst the portion above 

 is convexly shelving : at times the volutions are slightly 

 flattened above likewise, so as to appear subscalariform. 

 The base is a little compressed, yet tolerably convex : the 

 umbilicus, which is profound, rather large, and funnel- 

 shaped, has a somewhat abrupt commencement, and is at 

 times bounded by a spiral line. The aperture, which has 

 a roundish subquadrate contour, usually occupies half the 

 entire length, and half the basal diameter, of the shell. 

 Both lips are acute, simple, and arched ; the anterior 

 recedence of the projecting outer one is not considerable ; 

 the pillar, which is short, narrow, and very oblique, curls a 

 little towards the umbilicus. 



The basal diameter rarely exceeds the fifth of an inch in 

 native examples ; an individual of the smooth variety from 

 Greenland measured five lines across. 



The animal, which we have taken alive, and on which 

 Mr. Alder has communicated his notes, is entirely white or 

 yellowish white, with the exception of the black eyes and 

 dark spots at the base of the lateral cirrhi. The head 

 terminates in a broad crenated muzzle. The head-lobes 

 seem to be obsolete ; the tentacula are long, subulate, and 

 finely but conspicuously ciliated ; the eye-peduncles are 

 rather short ; the neck-lappets appear to be small ; there 

 are five lateral cirrhi on each side, three in the region of 

 the operculum and two anteriorly placed. The foot is 

 large, rounded in front, somewhat obtuse behind. 



On the British shores this Mollusk is confined to the 

 western and northern coasts of Scotland. It was first 

 described as a native by Mr. Lowe, who found it at Oban. 



