126 Mr. W. Clark on the Muricidte. 



thereon ; it is as large or a larger animal than the M. gracilis, 

 and if my memoiy is correct, it bears a close resemblance to it ; I 

 am certain it has no operculum, and that the emargination in 

 the outer lip is as conspicuous as in M. gracilis and M. teres. 

 Full-grown specimens are rare at Exmouth ; I have not obtained 

 one during the last two summers. It inhabits the coralline zone. 



Murex Smithii, nobis. 

 Plew'otoma Smithii, auctorum. 



Animal spiral ; ground colour white throughout, thickly mixed 

 with opake intense snow-white flakes, and on the siphon with 

 eight or nine bright pink spots, inhabiting a yellowish brown 

 plicated shell of nine volutions. The mantle is rather tumid at 

 the margin of the aperture, and is produced into a short, fleshy, 

 rather open or scoop-shaped branchial fold, which on the march 

 is carried somewhat beyond the termination of the canal ; it also 

 lines the anal sinus at the upper angle of the outer lip, which 

 some authors term a pleurotomic scission. The head is the usual 

 flat muricidal one, having at its centre the vertical Assure from 

 which the ordinary armed proboscis is emitted. The tentacula 

 are short, and the portions as far as the oft'sets, on which the 

 large black eyes are fixed externally, are thick and strong, but 

 the continuations are exceedingly short fine filaments. 



I consider the present, of all the species I have examined, as 

 that which has the eyes nearest the points. The foot is exactly 

 truncate in front, and scarcely eared at the external angles ; in 

 repose it is puckered and rounded posteally, but on the march 

 it extends to a sufficient lanceolate termination. There is no 

 longitudinal line on the sole, nor trace of an operculum ; it is 

 bevelled from the long pedicled base by which it is fixed to the 

 body laterally, and also slopes from the anteal truncature to a 

 sharp edge. 



The animal is rare at Exmouth, and inhabits the coralline zone ; 

 it is extremely free, and gives every facility for examination ; it 

 scarcely difiers from M. attenuatus, or the type, M. gracilis. 



It appears that the Murices of this section, none of which much 

 exceed an inch in length, are all without opercula, and have er- 

 roneously been considered the Pleurotomata of Lamarck, who 

 constituted the genus Clavatula for some of the species, but 

 afterwards abandoned it. The true Pleurotomata have all a deep 

 sinus or emargination in the upper angle of the outer lip of the 

 shell, and a corresponding scission in the mantle of the animal, 

 and the foot is invariably accompanied by an operculum. We 

 have shown that the British Pleurotomata are almost always 

 without opercula ; the genus has scarcely a malacological sup- 



