OTINA. 523 



and furnished with a creeping disk at each end, so that the 

 creature marches in the manner of Pedipes and Truncatella. 

 (The Chemnitzice have a very similar method of progres- 

 sion.) The branchial plume appears to lie across the head 

 under the centre of the mantle. 



We regard it as a very local shell, though tolerably 

 abundant when found at all. It is a strictly littoral 

 species, inhabiting the chinks of rocks between tide-marks, 

 where it is usually taken in the empty cells of barnacles 

 (^Balani) or attached to the common mussel, Mr. Clark 

 remarks that like the Littorina it is often uncovered by 

 the sea, for eighteen hours out of the twenty-four. It is 

 chiefly found on the western and south-western coasts, and 

 the rocky shores of the Irish Sea. Mr. Jeffreys finds it in 

 South Wales ; Mr. Clark in S. Devon ; Mr. Couch and 

 Mr. Peach in Cornwall ; Mr. Barlee in the Channel Isles. 

 On the east coast of England it has been observed in 

 Northumberland by Mr. Alder, and at Scarborough by 

 Mr. Bean. Mr. W. Thompson enumerates it among the 

 shells of the west coast of Ireland. Birterbuy Bay, Gal- 

 way (Barlee) ; Clare (Humphreys). 



It does not appear to have been noticed by continental 

 conchologists. 



