398 PYRAMIDELLID^E. 



and they are generally present in the Chemnitzits, 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- 

 n illa our Chemnitzia has not, though he has described the 

 animal of Eulima, 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 Chemnitzice of twenty 

 species, yet, except on the three occasions alluded to, I never 

 witnessed its exsertion. 



All the Chemnitzice 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 

 fascal 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 

 Rissoce ? Can it have the double, though apparently incom- 

 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 Eulimee 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; in the 

 Chem. unidentata it is plain and truncate, in C. acuta it forms 

 an open subcircular channel with a cochleariform termination, 

 and in Chem. conoiclea 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 



