TROCHUS. 323 



black) in the line of growth ; in some specimens the streaks 

 are interrupted and give a speckled appearance, or there is a 

 greenish tint, and in others the apex is reddish : sjpire bluntly 

 pointed: whorls 7, gradually enlarging, flattened, all but 

 the two apical ones, which are rounded : suture very slight and 

 inconspicuous : mouth obliquely squarish : outer Up rather thin : 

 inner lip short, broad and thick, undistinguishable from the 

 pillar ; it is slightly reflected above, and notched below by a 

 small blunt tubercular tooth, as in the last species: inside 

 silvery and iridescent, except towards the margin, where it is 

 frosty-white and thickened by an indistinct angulated rib ; 

 the young are slightly umbilicate : operculum as in T. Monta- 

 cutL L. 0-35. B. 0-3. 



Monstr. Scalariform ; whorls convex, each having a keel- 

 like ridge in the middle, and separated from the one next to 

 it by a deep suture ; base rounded. 



Habitat : Laminarian zone (especially on Zostera 

 marina), from low-water mark to 15 f.^, in the Channel 

 Isles^ Dorset, Devon, Cornwall, Cork, Baltimore, and 

 Bantry. Dublin Bay (Turton). The monstrosity was 

 found by Mr. Hockin at Falmouth, and by him kindly 

 presented to me ; it is similar to that of T. Montacuti. 

 The present species has only been noticed as fossil in 

 the Sicilian tertiaries (Philippi) . Recent on the coasts 

 of France, Portugal, Spain, Italy, Algeria, the Adriatic, 

 Madeira, and the Canaries, from the shore to 20 f 



The animal of this rather common species does not 

 appear to be known. The shell differs from T. Monta- 

 cuti in its larger size, remarkably flattened whorls and 

 base, and in having a greater number of spiral ridges. 



In all probability the T. striatus of Linne was in- 

 tended for the next species — if indeed that is not a 

 variety of the one which I have now described. Gmelin 

 and his followers named the present species T. erytkro- 

 leucos, Da Costa T. parvus, Donovan T. conicus, and 

 Deshayes T. depictus. 



