MUREX. 497 



but the animals are nearly identical, consequently we are bound 

 to consider the animal diagnoses of preponderating value, 

 and pronounce the two to be varieties of the same species. 



M. LINEARIS, Montagu. 



Mangelia linearis, Brit. Moll. iii. p. 470, pi. 114. f. 1, 2, 3; (animal) 

 pi. R.R. f. 6. 



Animal spiral ; the colour throughout is of a uniform bril- 

 liant frosted white, occasionally suffused with snow-white 

 opake matter. The mantle is simple, being only produced 

 into a simple branchial duplicature lining the canal of the 

 shell, and, as in its congeners, often extending beyond it. 

 The head is very short, flat, forming a sort of head-veil, under 

 which the usually armed proboscis issues ; consequently the 

 tentacula do not form a completely conjunctive angle at their 

 bases. 



I should have been glad to have seized and admitted such a 

 character as generic, in default of a better, to separate the 

 Pleurotoma and Fusus of authors, but I found the character 

 not constant, and that some of the more decided Pleurotomata 

 have the complete conjunctive tentacula, and not a trace of 

 head or head-veil, but merely the intervention of the usual 

 vertical buccal orifice. I am therefore compelled to relieve 

 the genus Murex of these modern dismemberments. I feel 

 confident that none of the so-called British Pleurotomata or 

 Fust differ generically from Murex. Some of the exotic species 

 may perhaps afford better distinctive generic indices. 



The tentacula are long, and taper to a fine point, having the 

 eyes at the external angles of pedicles of not half their length. 

 The foot in front is subtruncate, acutely auricled and labiated ; 

 when in action it is sinuated, long, narrow, tapering to a fine 

 point, and, when fully extended, reaches beyond the posterior 

 end of the spire. It is the only species I know of, except the 

 M. costatus, that shows this peculiarity. There is no vestige of 

 an operculum, and the lateral scission is rather more apparent 

 than in the two preceding species. The branchial plumes and 

 all the other organs are in exact accordance with the type, 

 M. gracilis. 



2 K 



