264 DR Johnston's descriptive catalogue of the 



separated by a smooth belt regularly spotted with pink ; apex 

 acute, purple ; base circularly striate, flattish ; aperture subquad- 

 rangular, the pillar concave, pearly. Height -A-ths ; the breadth 

 iVths. Billw. Eec. Sh. 799. 



Hah. Berwick Bay, not common. 



The shell is sometimes of a uniform white colour, when it has been described 

 as a distinct species under the name of " Trochus Lyonsii ;" and besides 

 this there are in onr Bay two varieties ; in one the whorls are slightly 

 concave, and the base is covered with the circular impressed striae ; in the 

 other the whorls are even, and there are only two or three stria) at the 

 pillar, and two near the margin, leaving the intermediate space perfectly 

 smooth. Operculum thin, round, and circularly striate. 



Snail of a more or less deep brown colour, which is often disposed in patches 

 or irregular streaks, covered with small tubercles, and furnished on each 

 side with four slender retractile filaments, originating from a free mem- 

 branous border that garnishes the sides, the back concave and smooth : 

 mouth shoi'tly proboscidiform, furnished with two smnll corneous jaws : 

 tongue long, linear, armed as usual with minute prickles arranged in 

 regular series : tentacula setaceous, pale, quadrangular, with a dusky line 

 along the upper angles, and rough with minute papillae when viewed through 

 a good magnifier : eyes on distinct pedicles at the external bases of the 

 tentacula : margin of the collar crenate or sinuate : foot oblong, tapered 

 posteriorly, the margin crenulate, the disk straw-yellow, more or less 

 tinted with red or flesh-colour. The edges of the foot can be brought 

 together so as entirely to conceal its disk. 



** Base umhilicate. 



2. Tr. cinerariiis, shell conical, obtuse, yellowish or bluish-grey, 

 ■with numerous narrow purplish stripes ; whorls six, flat, spirally 

 striate ; the base flattish and the umbilicus deep ; aperture white, 

 perlaceous, subquadrangular. Diam. of base -^^ ot iVths ; height 

 the same. Dilhv. Eec. Sh. 779. 



Hah. Between tide marks, veiy common. 



The spire is more or less raised, the suture more or less distinct, the base in 

 some more deeply striated than in others, and the umbilicus in young 

 shells wider than in the old, in which it is almost obliterated ; but among 

 these varieties there are none with characters sufficiently marked to justify 

 their elevation to the rank of species. Operculum circular, horny, thin, 

 concentrically striate, with a membranous border. 



The body and tentacula of the snail are finely marked with black transverse 

 lines, which become reticulated on the sides : tentacala two, slender, 

 setaceous : eyes on distinct footstalks at the external base of the tentacula ; 

 mouth striated with black lines, armed with a pair of oblong pointed car- 

 tilaginous jaws, and a ribbon-like tongue roughened with acute prickles 

 set in transverse curved lines ; sides of the body furnished with a ciliated 

 membrane, underneath which protrude several long tentacular filaments, 

 which issue from tubular sheaths, and are retractile : foot elliptical, 

 yellowish, the margin fringed with veiy short fleshy filaments, visible only 

 with a magnifier. Our childi-en call the shell Silver-hucl-ies or Silver- 

 ' Willies ; they do not eat the snail. 



During the summer we often find a spawn on the fronds of sea-weed deposited 

 in the form of a small ring, and of a cream colour. I believe this to be 

 the spawn of Tr. cinerarius. The ring is gelatinous, firmly adherent, and 

 contains innumerable ova, each separately laid in the centre of its own 

 gelatinous vesicle. 



