236 VELUTINID^. 



erect, but pressed downwards by the mantle : eyes black, placed 

 on extremely short offsets ; they are seldom visible from the 

 outside, in consequence of their being covered by the edge of 

 the mantle, but are exposed when the animal floats or swims : 

 foot large and long, squarish in front with a short triangular 

 lobe at each corner, bluntly pointed behind. 



Shell resembling in shape a very small Halioth without 

 holes (although it is more raised or convex), of a somewhat 

 membranous consistency, transparent when fresh, and of a 

 more or less iridescent lustre: sculpture, minute, irregular, 

 but distinct lines of growth, which are especially conspicuous 

 just below the suture, and more numerous microscopical spiral 

 striae, that sometimes become confluent and form stronger lines : 

 colour clear white, with occasionally either a darker or a paler 

 zone on the upper part of the body-whorl : spire oblique, 

 very small, placed near the end of the shell : luhorls 2|-o, 

 tumid, the last occupying eleven-twelfths of the spire (viewed 

 with the mouth downwards) ; the flrst whorl is apparently 

 semidetached from the next, and twisted: suture wide and 

 deep: mouth expanding outwards, exceeding in length five- 

 sixths, and in breadth seven-tenths of the shell ; its base is 

 entire : outer lip sloping from the periphery, with a curved 

 outline, but somewhat contracted ; edge thin : inner lij) nearly 

 semicircular, forming on the pillar a thin glaze, slightly stri- 

 ated lengthwise, and continuous with the upper edge of the 

 outer lip. L. 0-G5. B. 0-45. 



Male. Body white, with a few flake-white spots on the head, 

 yellowish with black spots, or plain dirty white : verge falci- 

 form. Shell much smaller and flatter, with the spire placed 

 somewhat less obliquely, and having a proportionally larger 

 mouth. 



Yar. lata. Shell smaller, broader, more compressed, but 

 not flattened as in the last form, nor contracted in front. 



Habitat : Adhering to the under surface of loose 

 stones, and in rock-pools, at low-water mark of spring 

 tides, in the laminarian zone, as well as in the coralline 

 and deep-sea zones down to 87 f. ; generally diffused 

 throughout our seas. Both sexes are found together. 

 I dredged the variety in deep water ofi' Unst ; it may 

 be tlie Bulla latens (Strom) of Miiller's ' Prodromus/ 



