MUKEX. 481 



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 Muricidfe, 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 inappreciable, 

 are the agents that effect the diversity of structure, sculpture, 

 and marking. 



M. MURICATUS, Mont. 



Trophon muricatus, Brit. Moll. iii. p. 439, pi. 111. f. 3, 4 ; (animal) 

 pi. 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 lip 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 Muricidce ; they are pointed 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 points minute auricles, 

 and tapering gradually to an obtusely pointed termination, 

 on which, at the upper surface, is a light, horny, suboval and 

 subimguiculated 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 Eulimus obscurus. 



2 i 



