398 PYRAMIDELLIDA. 
and they are generally present in the Chemnitzie, are to 
assist flexibility on the march, in the same manner as the 
digitations of the feet of all animals assist progression. 
Loven, who has described the mentum in his genus Turbo- 
nilla—our Chemnitzia—has not, though he has described the 
animal of Hulima, mentioned the presence of a mentum or 
rostrum in that genus. 
The point of issue of the proboscis, from the upper part of 
the rostrum, is more advanced and visible in Chem. plicata 
than in any other species I have yet examined; it was from 
this animal that it continued evolved more than three minutes, 
affording me a sight that falls to the lot of few malacologists. 
I believe I speak within compass, when I state, that I have 
examined more than a thousand live Chemnitzie of twenty 
species, yet, except on the three occasions alluded to, I never 
witnessed its exsertion. 
All the Chemnitzie have a semitubular fold more or less 
developed in the mantle, which, though it issues at the upper 
angle of the aperture, close to the debouchure of the rejecta- 
mental orifice, appears more like a branchial one than for 
feecal functions. In the true C. acuta it is largely exserted 
and very conspicuous. Can this fold be analogous to the 
process I have described at the same point in many of the 
Rissoe? Can it have the double, though apparently mcom- 
patible, duties of depuration, and to supply the animal, when 
the operculum on certain exigencies is required to be nearly 
closed, with the branchial fluid ? 
The presence of a proboscis brings this genus very near to 
the Canalifera; but the Hulime are still nearer, as they have 
no head or rostrum, and the proboscis issues nearly at the fork 
between the tentacula, as in the Muricidal families. 
The rostrum varies greatly in the proportions of its arcua- 
tions, scissions, and points of attachment to the foot; im the 
Chem. unidentata it is plain and truncate, in C. acuta it forms 
an open subcireular channel with a cochleariform termination, 
and in Chem. conoidea it is cloven nearly to the base, simu- 
lating a second pair of tentacula. 
I have omitted to remark, that the orifice of the rostrum is 
