RISSOA. 81 



sized and nearly equidistant spiral and longitudinal ridges, 

 so that the interstitial hollows are nearly square, or 

 somewhat broader than long. The spiral series on the 

 body-whorl are six or seven in number; of these two 

 or three are continued to the penult volution, and for 

 the most part two are likewise perceptible upon both 

 the preceding turns. The points of intersection, in living 

 examples, owing to the sharpness of the ridges in their 

 perfect condition, are acute. The body occupies from 

 one half to four-sevenths of the total length of the shell ; 

 its surface is moderately convex, and its basal declination 

 rounded and gradual. The spire is composed of four or 

 five short turns, of which the penult very nearly equals 

 the united length of the three previous ones ; they are 

 prominent, but not truly convex, and from their scalari- 

 form structure, the profound suture appears at times to 

 be almost canaliculated. The mouth, which is either 

 nearly ovate or of a rounded oval figure, occupies nearly 

 one half of the entire length, but its cavity is visibly 

 diminished by the thickness of the outer lip, which latter 

 is moderately curved and externally marginated and den- 

 tated by the projecting terminations of the spiral ridges. 

 The inner lip is often stained, in living examples, with 

 rufous chocolate ; with this hue the throat, which is 

 crenated by raised sulci, is also faintly tinged. The 

 pillar itself is arcuated, spread, and furnished with a 

 tubercular elevation. Our largest specimen measures 

 nearly a quarter of an inch in length, and more than the 

 eighth of an inch in breadth. 



The beach in a miniature bay of the little islet of 

 Herm, near Guernsey, is literally composed of myriads of 

 dead shells of this species ; yet during a residence of some 

 weeks not a single individual was discovered in a living 



VOL. HI. M 



