TROCHUS. 329 



the last whorl not so broad or large in proportion to the 

 rest. 



Monstr. Outer lip irregularly notched at its junction with 

 the penultimate whorl, like a Pleurotoma. 



HABITAT : Coralline zone, in Cornwall, Devon, Dor- 

 set, and the Channel Isles ; Isle of Man (Forbes and 

 Walpole); south and east of Ireland (Turton and others); 

 Belfast Bay, " two broken specimens, but probably in- 

 troduced accidentally " (Hyndman) ; 50 f. off the Mull 

 of Galloway, and living at a depth of 145 f. in Beau- 

 forf s Dyke, the species having been determined by the 

 late Mr. William Thompson of Belfast (Beechey) . The 

 varieties and monstrosity are from Exmouth. Lamarck 

 says it is found fossil in England; but he was pro- 

 bably misinformed. I do not agree with Mr. Wood 

 in considering the Red Crag shell, which he named in 

 his catalogue T. granosus, to be a variety of our recent 

 species. Whether it was the progenitor of T. granula- 

 tus is another question. The fossil species is much 

 smaller and more solid ; it never has an incurved out- 

 line towards the apex, or a prominent tuberculated 

 ridge on each whorl ; and the spire is more depressed. 

 Mr. James Smith has enumerated the present species 

 as an Irish fossil, Mr. Woodward as occurring at Bra- 

 merton and Thorpe in the Norwich Crag, and Brocchi 

 from Piacentino. It is not uncommon on the coasts of 

 France, Spain, Italy, Algeria, Madeira, and the Cana- 

 ries, at various depths ranging from 4 to 60 f. 



This handsome shell is frequently procured by trawl- 

 ing. The fry has the first whorl smooth, and the 

 second regularly and strongly cancellated ; and it ex- 

 hibits a conspicuous and rather deep umbilicus. The 

 lingual ribbon is comparatively short; its outer ex- 

 tremity is covered by two large, oval, horny jaws. 



