340 LITTOEINID^. 



conchologically appear to be Rissote, inhabit only the coralline 

 zones, and as most of the animals are unknown, the true rela- 

 tions between the animals of the littoral and coralline districts 

 are not as yet satisfactorily ascertained. 



Littorina has only four species, L. littorea, L. rudis, L. neri- 

 toides y and L. littoralis. 



LITTORINA, Ferussac. 

 L. LITTOREA, Linnaeus. 

 L. littorea, Brit. Moll. iii. p. 29, pi. 83. f. 7, 8 ; (animal) pi. G.G. f. 3. 



This exceedingly common, but very curious and interesting 

 animal, has not met with the attention it deserves ; we are 

 sure that we shall afford gratification in producing a detailed 

 account of it. 



Animal spiral ; mantle simple, exactly lining the aperture 

 of the shell. The head is long, cylindrical, not deeply cloven ; 

 mouth a vertical fissure, and with the neck and tentacula 

 marked on their upper surfaces, on a yellow ground, with very 

 close-set, dark transverse lines, which, with the lead-coloured, 

 anastomosing, longitudinal waved markings, give the animal 

 almost a black appearance. The tentacula are moderately 

 long, conical, pointed, very tumid at their bases, black above, 

 white beneath, on which the eyes, a little raised, are set ex- 

 ternally. The foot is a very singular organ, short, rounded 

 before and behind, scarcely auricled, and when in action 

 forming an oblong suboval disk, divided by a central sunken 

 line into two longitudinal lobes, which, when the animal 

 marches, are each advanced alternately with an undulating 

 vermicular motion. This curious longitudinally-divided foot 

 and peculiar locomotion are only to be found in one or two 

 other genera ; they are particularly conspicuous in the Phasia- 

 nella pullus. The under part of the foot is yellowish- white, 

 bordered by a deep line at a little distance within the margin, 

 from which fine transverse ones radiate, giving the foot the 

 appearance of being encompassed by a fine fringe ; the upper 

 posterior part carries a dark, corneous, suboval operculum, 

 with about two turns of elliptical striae, and a very excentric 



