1 1 2 Mr. W. Clark on the JMuricidse. 



generally be of a deeper red, somewhat rounder, though the arches 

 of the stria? are no less elliptical. The gland producing the pur- 

 ple dye is as conspicuous as in M. lapillus ; indeed this gland 

 may be traced in all the Canalifera, though its secretion varies 

 in colour ; there may also be a slight difference in the lingual 

 riband, which is here rather longer and more coiled than in its 

 congener, and the cerebral ganglions smaller, but these varia- 

 tions are of little value. The different hues of brown in Murex 

 erinaceus form the ground colour, but are invariably mixed with 

 white or flaky yellow markings on the upper part of the foot 

 and on the tumid portion of the tentacula, the conically pointed 

 upper parts being of a uniform colour ; the under part of the 

 foot is bordered by a narrow band of flake-wbite transverse fila- 

 ments : these distinctions in the coloration are constant. 



This species inhabits the littoral, laminarian, and coralline 

 zones in abundance at Exmouth. It may be asked, what are the 

 causes that animals of such decidedly similar organs, as the 

 Muricidce, should produce shells so entirely dissimilar ? The 

 answer is, that there are certain variations in the form and dis- 

 position of the vessels of the mantle for the secretion of the cal- 

 careous and colouring matters which are inappreciable, and are 

 the agents that effect the diversity of structure, sculpture and 

 variation of the markings. 



Murex muricatus, Montagu et nobis. 



Animal of seven or eight spiral volutions, of a pure white 

 ground interspersed sparingly in some specimens with intenser 

 minute white flakes ; the mantle is even with the aperture, ex- 

 cept that it is prolonged into a branchial fold, often extending 

 beyond the canal of the shell ; there is no emargiuation in the 

 upper part of the outer lip of the shell, but only a small inci- 

 pient duct, which is lined by a corresponding extension of the 

 mantle. The head is the usual flat, little-produced characteristic 

 organ of the tribe ; the mouth is a central vertical fissure that 

 exserts the usual proboscis ; the tentacula are pointed and rather 

 long in propoi'tion to the minute size of the animal, with eyes on 

 external offsets at about half their length. The foot is of mode- 

 rate length, a little curved anteally, forming at its right and left 

 points minute auricles, and tapers gradually to an obtusely 

 pointed termination, on which, at the upper surface, is a light 

 hoi'uy 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 en- 

 veloped in an orange-red spongy mass, which doubtless serves as 

 a mantle of concealment and protection in like manner as the 

 earthy coating of the land Bulimus obscurus. 



