Mr. W. Clark ow the Muricid^. 117 



The colour of the upper part of the foot, of the tentacula as far 

 as the eyes, and of the branchial fold is a light brown ground, 

 so thickly studded with yellow flakes and minute dark points and 

 blotches as to give the animal a dark pepper-and-salt aspect ; the 

 under part of the foot is yellowish brown, aspersed with very 

 minute dark points. The head is small and flat, with two long 

 tentacula bearing eyes externally on ofi"sets about a quarter 

 of an inch from the bases, where they are wide, but from thence 

 to their termination they become slender and pointed. The foot 

 is very large, long and broad, extending when in full march more 

 than the length of the shell; it is bevelled to a fine edge, gently 

 rounded, indented in the centre in front, and has slightly curved 

 rather long auricles ; it then gradually declines to an elongated 

 lanceolate termination, which is emarginate and sends forth from 

 each fillet of the fork a pointed filament ; close and anterior to 

 the caudal cmargination is a brown, corneous, suboval, subun- 

 guiculated operculum. I have thought that the cmargination 

 might be the seat of a gland, as that part is constantly covered 

 with mucus, which, when removed, recurs ; but as I could trace 

 no distinct duct, I presume the exudation is of porous origin. 

 The mouth is a vertical fissure under the head, from which a 

 very long proboscis is protruded, the architecture whereof is in 

 all respects similar to that of Murex undatus, mihi (the Bucci- 

 nutn undatum, auctorum), as are the cerebral ganglia, the salivary 

 glands, the double branchial plumes, the mucous fillets, and the 

 heart and auricle ; all these organs I have dissected and compared 

 with the same parts of that species, and I found no essential 

 differences. 



It appears from these notes that the principal variations of 

 this section of the Muricidal group from its fellow-species con- 

 sist in the large size and somewhat varied outline of the foot 

 with its caudal filaments ; but surely no malacologist will contend 

 that these are generic distinctions : the whole of the animal must 

 be taken into view, which will undoubtedly, with all disinterested 

 naturalists, stamp it as a true member of the genus Murex. This 

 animal is lively, active, not at all shy, and marches with rapidity ; 

 it inhabits in great abundance the littoral and laminarian zones. 

 It must be regarded as the type of the British species of this 

 section ; it has the most intimate and congeneric alliances with 

 the animals of the third and fourth sections. 



Murex incrassatus, nobis. 

 Buceinum macula, Montagu. 

 Nassa incrassata, auctorum. 



Animal spiral, throughout of a pale dirty yellow, marked irre- 

 gularly on all its organs with small dark lead-coloured or brown 



