CERITHIOPSIS. 867 



obtusely triangular, and is often carried (as lias also been 

 observed by Dr. Knapp) considerably beyond tbe head ; 

 this, though usual in swimming, we observed not to be so 

 frequent in walking. Beneath it is marked with a very 

 deep median groove, terminating in a perforation; dorsally 

 and caudally it carries on a simple lobe a corneous sub- 

 unguiculated suboval corneous operculum resembling that 

 of EiiUma polita, except that the upper angle is rounded 

 instead of being pointed. The general colour is white, 

 with dusky markings ; in our specimen the tentacles were 

 banded, or ringed with lead-colour. The head and anterior 

 half of the foot are dark. Some specimens are flake white, 

 except some sulphur-yellow points behind the eyes, and 

 behind them, on each side of the neck, a band of minute 

 brownish-red points ; also two sulphur-yellow patches, one 

 on each side of the operculum. 



This shell, which dates as a British species as far back 

 as the coralline crag epoch, has a similar distribution with 

 reficulatum, though it is much scarcer. We have taken 

 it alive, in from four to ten fathoms among ::ostera on the 

 west coast of Ireland (E. F., R. Ball, W. Thompson) in 

 eighteen fathoms on the west bay of Portland (E. F. and R. 

 M'Andrew), and Lieutenant Thomas has found it ranging 

 from seven to forty fathoms among the Orkneys and Zet- 

 lands. Mr. Clark found it at Exraouth in the middle levels 

 of the littoral zone, in quiet sheltered pools on the smaller 

 algaj ; and Mr. Jeffreys at Falmouth, Tenby, Fishguard, 

 Bantry Bay and Cork. Mr. Barlee found it at Gruernsey, 

 also at Oban and Loch Fyne; north west and south of 

 Ireland (W. Thompson). It is a lively animal. 



It ranges to the Mediterranean. 



