RISSOA. 79 



and the slight anterior or terminal keel. Sometimes the 

 spiral sculpture is comparatively obscure, so as to be 

 chiefly perceptible through intersectional asperities upon 

 the perpendicular ribs. There are six and a half abruptly 

 scalariform volutions, that are so deeply divided by the 

 profound yet simple suture, towards which they suddenly 

 and subangulately shelve both above and below (the middle 

 portion being moderately convex), as almost to appear dis- 

 united. The length of the body is about equal to that of 

 the spire, and the length of the penult to that of the two 

 previous turns united ; the apex is exceedingly small in 

 proportion to the next two equally smooth volutions. The 

 m<?uth occupies from about two-fifths to nearly three- 

 sevenths of the entire length, and is oval or rounded oval, 

 and not crenated internally. The outer lip is solid, 

 arcuated, prominent, and thickened behind by a sharply- 

 projecting but not very wide rib ; It Is curiously edged with 

 two erect lines, enclosing a very narrow and flatly exca- 

 vated space between them, the Inner one of which passes 

 over the plllar-llp, and completes the circuit of the 

 aperture. Our largest specimens were only a line broad, 

 and scarcely two in length. 



We have never seen It alive. 



Though designated after our northernmost province, this 

 species really occurs at both ends of the British seas, 

 but Is scarce and local. Herm (S. H.) ; Guernsey (Bar- 

 lee) ; Exmouth, where It was gathered by Mr. H. Gwyn ; 

 In Barry cane, North Devon, collected by Miss Jeffreys 

 (Jeff'reys). In thirty-five and seventy fathoms on the 

 west coast of Zetland (M 'Andrew and E. F.) ; Lerwick 

 (Jeffreys and Barlee) ; Eda Sound, and In from twenty 

 to fifty fathoms on the east, and forty to sixty fathoms on 

 the west coast of Orkney (Thomas). 



