MUREX. 48] 
bordered by a narrow band of flake-white transverse filaments. 
These distinctions in the coloration are constant. 
This species inhabits the littoral, laminarian, and coralline 
zones at Exmouth in abundance. It may be asked, what are 
the causes that animals with such decidedly similar organs as 
the Muricide, should produce shells so entirely dissimilar? The 
answer is, that there are certain variations in the form and 
disposition of the vessels of the mantle for the secretion of the 
calcareous and colouring matters, which, although appreciable, 
are the agents that effect the diversity of structure, sculpture, 
and marking. 
M. muricatus, Mont. 
Trophon muricatus, Brit. Moll. ii. p. 439, pl. 111. f. 3,4; (animal) 
pl. S.S. f. 5. 
Animal of seven or eight spiral volutions, of a pure white 
ground interspersed sparingly in some specimens with minute 
flakes of a more intense white. The mantle is even with 
the aperture, except that it is prolonged into a branchial 
fold, often extending beyond the canal of the shell. There 
is no emargination in the upper part of the outer lp of 
the shell, but only a small incipient duct, which is lined 
by a corresponding extension of the mantle. The head 
shows no trace of a muzzle. The tentacula coalesce, as in 
the strict Muricide; they are poimted and rather long in 
proportion to the minute size of the animal, with the eyes 
on thick offsets at about half their length. The buccal 
orifice is a central vertical slit, and exserts a retractile pro- 
boscis. The foot is of moderate length, a little curved 
anteally, forming at its right and left pomts minute auricles, 
and tapering gradually to an obtusely pointed termination, 
on which, at the upper surface, is a light, horny, suboval and 
subunguiculated operculum. 
This beautiful species is taken abundantly alive at Exmouth 
in the deepest waters of the coralline zone ; it is almost always 
enveloped in an orange-red spongy mass, which doubtless 
serves as a mantle of concealment and protection, like the 
earthy coating of the terrestrial Bulimus obscurus. 
21 
