498 MURICIDZE. 
The shells exhibit two well-marked varieties; the one the 
typical M. linearis, with more regular subdued spiral striz ; 
the other is more scabrous. The smoother variety is sparingly 
found in the coralline zone; the scabrous shells are abundant 
in the same zone, at Exmouth. I have only examined the 
animal of the latter; it is possible the former may be distinct. 
—Exmouth, 3rd August 1850. Since writing the above I have 
met with a fine live specimen of the smoother variety, and I 
am unable to detect a variation in them. 
M. arrenvatvs, Montagu. 
Mangelia attenuata, Brit. Moll. ii. p.488, pl. 113. f.8,9; (animal) 
pl. R-R. £..5. 
This beautiful species is mm most respects so similar to the 
Murex gracilis, the type of this section, that to describe it 
would be nearly a literal repetition of the account of that 
animal, except that the emargimation of the outer lip, which 
scarcely merits that term, is rather a minute hollow shoot 
than a scission: there is no operculum. ‘This is a rare ani- 
mal, but I have examined several from the coralline zone at 
Exmouth. 
Another variation from the M. gracilis is, that the foot, 
when fully extended, is as long as the shell; it is bordered 
with flake-white spots, but no pmk marks are mixed up with 
it either below or above, as in M. gracilis. In this species 
the only pmk or red spots are on the termmation of the 
branchial fold. The organe générateur is of a pea-green 
colour, and in other respects is precisely similar to that of 
the type. 
No head-veil or inflation imterferes with the coalition of 
the tentacula. 
M. costatus, Montagu. 
Mangelia costata, Brit. Moll. i. p. 485, pl. 114 A. f. 3,4,5; (animal) 
pl. R.R. f. 4. 
Animal spiral, of seven or eight turns, of a pale hyaline 
ethereal blue nearly throughout, shaded with the most delicate 
white. The mantle is of the general ground colour, and even 
with the shell, except the shght depuratory fold which lies in 
