SCALARIA. 461 
animals; the spiral operculum, single branchial plume, and 
almost entire aperture, indicate their relation with the Litto- 
rine, whilst the mucous fillets and prominent retractile pro- 
boscis, the latter a character of the highest value, fix them 
amongst the immediate points of transition to the Muricide. 
S. ctatHratTuLa, Montagu. 
S. clathratula, Brit. Moll. ii. p. 209, pl. 70. f. 3, 4. 
Animal occupying a densely plicated, milk-white, spiral shell 
of 9-11 volutions. The animal nearly throughout is bluish- 
white, aspersed at the points of the tentacula, on the head and 
neck, and margins of the foot, with blotches and spots of 
snow-white matter. Mantle fleshy, reflexed on the peripheral 
rib of the aperture, and forming also a short, lax, branchial 
fold to correspond with the incipient canal of the shell. The 
head, though very short, is distinct, compressed and crescent- 
shaped, as in Murex; beneath slightly emargmate in the 
centre, at which point is the mouth, which is partially, trans- 
versely and vertically cloven ; from this a long, strong, fleshy 
proboscis is exserted, which I have repeatedly seen evolved 
several times in a minute. The tentacula are moderately 
long, divergent, subcompressed, with blunt terminations. The 
eyes are very black, not fixed on offsets, but on scarcely raised 
eminences or decidedly external semicircular inflations which 
are integral parts of the bases of the tentacula. The foot can 
be extended beyond the tentacula; it is nevertheless short, 
narrow, and bevelled on both sides, arcuated gently im front 
when on the march, and slightly auricled ; at rest subtruncate ; 
it is also grooved transversely in front, dividing the sole from 
the upper part, and forming a distinct labium, the sole being 
somewhat the longest ; it tapers to a slender, rounded termina- 
tion, carrying at some distance from the extremity, on a simple 
lobe, a white, spiral operculum of three turns; the first two 
are very small and eccentric, the third rapidly creases and 
occupies ;°,ths of the area, and is marked with elliptical strize 
of increment. The posterior half of the foot is deeply grooved 
longitudinally and medially in the sole with a central depres- 
