MUREX. 493 
all the organs with intense-white flakes, mixed nearly equally 
with pink lines, points and blotches ; these are minute, though 
varying in size and irregularly distributed. Mantle rather 
thick, not extending beyond the margin of the aperture, 
except the branchial fold, which is often carried considerably 
beyond the canal of the shell; it also forms in the outer lip, 
at the upper part, a small, open, slightly produced conduit 
that lines a deep scission in that part of the shell. This spe- 
cies is one of the most typical of the Pleurotomata of British 
authors, but its distinguishing feature, the sinus, is not suffi- 
ciently stable in the British species to give them the impress 
of generic distinction. 
The head is a short red protrusion, vertically cloven, evolving 
a long proboscis ; it contains the usual short spiny tongue and 
other organs of the buccal apparatus ; consequently in this spe- 
cies the tentacula do not completely coalesce basally. The want 
of conjunction of the tentacula at their bases is the character 
principally relied on by those malacologists who contend for 
a generic distinction between the so-called Fusus and Pleu- 
rotoma; but this character as regards the British Plewro- 
tomata is very variable and cannot be depended on, as 
some decided ones have not a trace of an exserted head or 
veil, and have their tentacula conjunctive at the bases, with 
only the separation of the proboscidal fissure; and in the 
genus Fusus the same discrepancies occur, as in some of the 
minor species the tentacula coalesce, whilst in others the con- 
junction is slightly mtercepted by the scarcely appreciable 
appearance of a head or head-veil. The tentacula in the 
present animal are short, with eyes on the external extre- 
mities of offsets which extend within a very short distance of 
their points. The foot at rest is beautifully puckered ; when 
in action it is truncate in front, with small auricles, fiat, long, 
acuminated behind, and extending to the fourth volution from 
the base. There is not a trace of operculum: it is difficult to 
account for the absence of this appendage ; it may be surmised 
that the apertures of these shells are so narrow as not to 
require such a protection, but this argument cannot be relied 
on, as we see that the Aporrhais pes pelecani has a corneous 
