MELAMPUS. 105 



and varnish -like, pale yellowish : spire short, although rather 

 slender, ending in a blunt and obliquely twisted apex : whorh 

 6-7, rounded and slightly convex, compressed towards the 

 suture, and partly overlapping one another or imbricated; 

 the last occupies about three-fourths of the shell : sutu7'e slight 

 but distinct, sometimes eroded and irregularly defined: 

 mouth contracted towards the top, and expanding below ; it 

 equals in length that of the remaining portion of the shell : 

 outer lip having a thin edge, somewhat flexuous at the upper 

 end, thickened and smooth inside, and bevelled outwards : 

 inne}' lip filmy, broad, and reflected below : pillar thick, with 

 two strong white folds, the smaller one twisted and near the 

 base, and the larger one placed a little above it. L. 0-22.5. 

 B. 0-1. 



Var. alba. Smaller, narrower, and thinner. Voluia alba, 

 Turt. Conch. Diet. p. 250 (not V. alba of Montagu, which is 

 a tropical species of Marginella). 



Habitat : Under stones that lie close to the ground, 

 between tide-marks, on many parts of oni' coast from 

 Shetland to Sark, as well as round Ireland. The variety 

 is equally diflFiised. M. bidentatus has been found 

 in the north and west of France, the Mediterranean, 

 and Adriatic ; and Mr. Watson sent it to me from Ma- 

 deira. 



It probably feeds on decaying seaweeds. When 

 crawling under water the tentacles are withdrawn, as 

 in the land-snails and slugs. Its locomotion is very 

 slow, in consequence of its using alternately the front 

 and hinder lobes into which the foot is divided. Mr. 

 Clark for this reason considered it a Pedipes ; but from 

 Adanson^s account the mode of progression in that mol- 

 lusk must resemble the ^' looping '' action of some cater- 

 pillars, the middle portion of the foot being hollow and 

 widely separating the lobes. The shell of Pedipes is 

 generically different from that of Melampus. I counted 

 in a minute no less than 132 pulsations of the heart 

 in a specimen of M. bidentatus, 



r 5 



