CERITHIUM. 11)9 



granular by numerous slanting longitudinal costellar lines, 

 which form a rather depressed clathration in their intervals, 

 traverse the whorls ; one lying rather above the middle, 

 one towards the top, and the third half-way between the 

 subcentral one and the lower suture. The two lower ones 

 are both larger and more projecting than the less distinct 

 upper one, and this, coupled with a slight filiform sub- 

 margination of the base (eventually appearing upon the 

 body as a fourth subgranose or undulated ridge, below 

 which the shell is horizontally compressed, and either 

 smooth or merely marked with faint continuations of the 

 longitudinal sculpture) gives a kind of subimbricating look 

 to that portion of the volution, and causes the posterior 

 end of the succeeding whorl to seem slightly concave. 

 The mouth, exclusive of the rather short but decided and 

 prominent canal in which it terminates anteriorly, and 

 which bends abruptly to the left, is somewhat squarish in 

 shape, rather longer than broad, and very small, occupying 

 merely a fifth of the entire length, and about one- half only 

 of the basal diameter. The outer lip is simple, acute, 

 and nearly straight, forming an angle with the scarcely 

 convex basal margin. The pillar is short, and devoid 

 of sculpture, but is slightly raised at its anterior edge. 

 The throat is apparently smooth, except from indentations 

 caused by the external ridges. A third of an inch in 

 length, and a tenth of an inch in breadth are the dimen- 

 sions of our largest perfect example, but fragments in- 

 dicate the attainment of the species to a somewhat larger 

 size. 



It was first dredged in fifty fathoms water between 

 Fair Island and the mainland of Zetland (E. F. and 

 R. M'Andrew). It has also been taken in eighty-two 

 fathoms on the east coast of Zetland. 



