CERITHIOPSTS. 267 



becomes suddenly very much narrower, and consists of 4 or o 

 whorls ; apex twisted a little downwards : whirls 13-14, com- 

 pressed, the last exceeds one-third of the shell : suture nar- 

 rowly channelled : mouth oval, truncated at the base ; its 

 length, with respect to that of the spire, is as 2 to 7 : canal 

 nearly tubular, and exhibiting outside a deep and rounded 

 notch at the base — quite different from what appears in any 

 species of Cerithmm: outer lip semicircular and rather promi- 

 nent, having a thick edge, which is scalloped by the spiral 

 ridges ; inside smooth ; this lip is contracted at the upper cor- 

 ner of the mouth into a small sinus (formed by an indentation 

 of one of the ridges), but it does not retreat or slope backwards 

 as in C&riihium perversum : inner lip rather broad, forming a 

 rather thick fold on the lower part of the pillar, and continu- 

 ous with the outer lip at the upper corner : pillar extremely 

 short, and nearly straight : operculum thin, marked with very 

 delicate and minute iiexuous striaB ; spire excentric, minute. 

 L. 0-25. B. 0-085. 



Var. nana. Dwarf and spindle-shaped. (Is this the male ?) 



Monstr. Clarlcii. Lower and middle whorls having but two 

 rows of tubercles, all of which are oblong ; the earlier whorls 

 have the usual number of rows. 



Habitat : Under stones in the lower part of the lit- 

 toral zone, and hard ground in the laminarian and 

 coralline zones, along onr southern and western coasts, 

 including the Channel Isles, Bristol Channel, and St. 

 George's Channel, all Ireland, the west of Scotland, and 

 Shetland ; Sandwich (Roys, fide Montagu) . The variety 

 is from Guernsey, Bantry Bay, and other places. The 

 monstrosity was taken by Mr. Clark at Exmouth, and 

 by me at Guernsey. Fossil: " Ireland; Clyde" (J. 

 Smith) ; Coralline Crag at Sutton (Wood) ; Belgian ter- 

 tiaries (Nyst). Its extra-British habitat ranges from 

 Christiansund (Lilljeborg), southward to Fayal in the 

 Azores (Drouet), and throughout the Mediterranean 

 and Adriatic, at depths of from ] to 60 f. ; Charlestown 

 Harbour in South Carolina (C. B. Adams, as Cerithium 

 Greenei) . Malm found a specimen of the monstrosity 



n2 



