BY C. MEDLEY. ' 715 



crawls over the mud at a fair pace; if placed in a vessel of sea- 

 water, it soon creeps out, and always moves steadily away from 

 the light. 



The foot is small and narrow for the size of the shell: there 

 is no operculum. The facial area is darker in colour, and covered 

 with finer tubercles than tlie rest of the animal; it is marked off 

 from the foot bv a groove on each side. When the animal is 

 extended, the tentacles are planted well apart, but seem to spring 

 from contiguous bases when it is contracted. They are sub- 

 cylindrical, slightly tapering, blunt at the tips, contractile, not 

 evaginate. The eyes are sunk within tlie substance of the 

 tentacle. Near the tip of the muzzle are two, white, oblong 

 marks that may represent the smaller tentacles of the Helicidse. 



The muzzle is unusually broad, being as wide as the foot. 

 Sometimes it is emarginate in front, and usually recurved at the 

 margins. The mouth is in the centre of a large, labial disc. 

 Between this disc and the fore-part of the foot is a shallow pouch. 



SiPHONARiA SCABKA Reeve. 

 (Plate 1., tig.32.) 



Siphonaria scabra Reeve, Conch. Icon., ix., 1856, Pl.i., fig. 2. 



This species occurs on sheltered rocks at low water. It does 

 not cling as firmly to the rock as a limpet does, and, when upset 

 on its back, finds more difficulty in turning over. On the right 

 is a free lobe of the mantle, sometimes rolled in a funnel or spread 

 in a flap, and reaching to the edge of the shell. The head is 

 devoid of any trace of tentacles; the eyes are small, and sunk 

 under the surface. The muzzle is spotted with black; it projects 

 a little past tiie foot, and terminates in a broad, mobile, upper 

 lip, which may assume a notch in front and recurved corners at 

 the side. Beneath it is thn mouth. The foot is spotted on the 

 side and is of the ordinary limpet-shape. 



Hhizorus. 



Ehizorus Montfort, Conch. Syst., ii., 1810, p.3.39, PI. Ixxxv., 

 for R. addaidis M.ontiort,r^ Bulla acrtminato Bruguiere, 1792. 

 Volvula A. Adams, in Sowerby, Thes. Conch., ii , 1850, pp.558, 



