486 MURICIDAL. 
We have obtained a fine series of the shells of the 17. Hum- 
phreysianus, and believe it to be a smooth variety of this most 
variable species. The Buccinum acuminatum of authors is 
generally considered a flat-whorled variation of the ‘“unda- 
tus ;” at present we accept that position, though with some 
doubt, on account of the peculiar compressed character of the 
volutions in the three examples we have examined. The 
animal must decide the question. 
Sectio IV.—Testa tumida, levis, sepe spiraliter substriata. Canalis ob- 
liquo-dorsali-brevissimus. Apertura ovalis. Columella dorso-fastigiata. 
Operculum corneum. 
Purpura, Lamarck et Auct. 
M. vapituus, Linneus. 
Buccinum lapillus, Montagu. 
Purpura lapillus, Lamarck et Brit. Moll. iii. p. 380, pl. 102. f. 1, 2, 3; 
(animal) pl. L.L. f. 4. 
Animal spiral, of a uniform pure white or pale yellow, 
without the intermixture of other colours or markings, 
except a single superficial fine longitudinal line of deeper hue, 
which divides the under part of the foot into two portions. 
The mantle is of very thin texture, liming the shell only to the 
margin, except the part constituting the branchial fold, which 
is occasionally carried, in marching, a little beyond the short 
canal. The head is very small, slender and flat; from this 
spring the moderately long tentacula, which are tumid and 
rounded from their bases, accompanied for two-thirds of their 
length by offsets on which the eyes are placed externally, and 
from thence running conically to not very pomted termina- 
tions; the mouth and its vertical fissure, from which a short 
proboscis is very rarely seen protruded, are beneath. The foot 
when at rest is nearly oval, but in action it is truncate and 
auricled in front, somewhat attenuated in the middle, and has 
a rounded termination, with, on its posterior upper surface, 
an irregular oblong, red-brown, corneous, subunguiculated 
operculum, having the lines of increment raised on the inner 
surface. The buccal mass, as in all the Murices, lies within 
