418 MURICID.E. 



that the left basal outline is deeply incurved : the anterior 

 declination is rounded, but rather gradual. The mouth, 

 which fills one-half of the entire length, and is generally of 

 a shining porcelain white, and devoid of all sculpture, is 

 acutely contracted above, and of an oblong-oval figure that 

 is produced below in a rather broad and gently reflected 

 oblique canal. The outer lip is simple, very sharp-edged, 

 not at all patulous, only moderately projecting, gently 

 arched above, and slightly retuse or straightish anteriorly. 

 The pillar is smooth and lustrous, has rarely a very thick 

 layer of enamel, is of a rich flesh-colour in the darker 

 individuals, and is sinuous in outline, being deeply concave 

 in the middle, but bending ofi" obliquely and subrectilinearly 

 at about one-third of the distance from the tij) of the 

 canal. 



The average size of examples is from about two inches 

 and a-half by thirteen lines, to three inches in length, and 

 one and a-quarter in breadth. We have chiefly drawn up 

 our description from the beautiful slender form that is most 

 commonly preserved in cabinets. There are, however, 

 many varieties of this interesting shell, among which two — 

 in which the outer lip is peculiarly arcuated, and the enamel 

 thickly spread on the columellar lip — may more particularly 

 be specified ; the one, a large thin ventricose form, dredged 

 from the Doggerbank, at a depth of fifty fathoms ; the other, 

 a very coarse and solid-ventricose form from Brixhani, in 

 which the costellffi of the smaller turns are well raised, and 

 the whorls are nine in number : this we take to be the 

 typical Islandicus figured in Chemnitz. 



The animal is of a general dull yellowish- white hue ; the 

 sides of the foot, when at rest, are greatly corrugated ; 

 its anterior extremities are obtusely angulated, the caudal 

 one rounded and bearing the operculigerous lobe very far 



