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. tinearis, Montagu. 
Mangelia linearis, Brit. Moll. iii. p. 470, pl. 114. f. 1, 2, 3; (animal) 
pl. R.R. f. 6. 
Animal spiral; the colour throughout is of a uniform bril- 
hant frosted white, occasionally suffused with snow-white 
opake matter. The mantle is simple, bemg 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 Plewrotomata ov 
Fusi 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 poimt, 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 smuated, 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. 
2K 
