PLEUROTOMA. 393 



whole surface (except the apex, which is smooth and glossy) 

 is covered with numerous and fine spiral striae or lines, many 

 of which are double ; the spiral striae or lines on the ledge or 

 shelf below the suture are slighter and obscure, the strongest 

 being those on the upper whorls ; they are nowhere decussated 

 by the microscopic iines of growth : colour purplish-brown, 

 the ribs being frequently paler ; inside of the mouth occasion- 

 ally of a rich purj)le : spire turreted, and regularly tapering ; 

 apex twisted : whorls 7, rather convex, shelving abruptly to 

 the suture, so as to give the turreted aspect to the spire ; the 

 last whorl occupies three-fifths of the shell: suture rather deep: 

 mouth shaped as in P. septangular Is, but not so acute-angled 

 above ; length two-fifths of the shell : canal as in the last 

 species, except that the basal notch is more rounded : outer lip 

 arched, with a thin and even edge ; it is slightly angulated 

 above : labial notch small, but distinct, forming an indentation 

 in the infrasutural shelf: inner lip somewhat expanded, and 

 presenting a polished appearance : pillar broad and fiexuous : 

 operculum ear-shaped, and elongated, marked lengthwise by a 

 furrow on the pillar side ; layers of increase numerous and 

 obliquely curved. L. 0*5. B. 0*2. 



Yar. 1. lactea. Body milk-white; jpallial tithe short and 

 rather broad : tentacles cylindrical, very short and club-shaped 

 above the eyes, much thicker below them : eyes proportionally 

 large, on the top of stalks which are amalgamated with the 

 tentacles : foot rounded in front, with small angular corners, 

 bluntly pointed behind. Shell milk-white. 



Yar. 2. semicostata. Lower whorls ribless ; shell often 

 larger than the usual size. 



Yar. 3. Ulideana. Shell orange-brown or fawncolour, with 

 stronger sculpture. P. Ulideana, Thompson in Ann. & Mag. 

 N. H. XV. p. 316, pi. xix. f. 2. 



Yar. 4. Cranchii. Ribs twisted. Fusus Cranchii, Brown, 

 111. p. 6, pi. V. f. 5. 



Yar. 5. anc/usta. Shell narrower, and slender, with sharp 

 and oblique ribs. 



Habitat : Sand in the laminarian and coralline zones^ 

 on our eastern, southern, and western coasts, the Bristol 

 and St. George^s Channels, all round Ireland, and the 

 west of Scotland; Scarborough (Bean and J. G. J.) ; 



s5 



