CHEMNITZIA. 431 



discovery of the species I neglected to enlarge them ; I have 

 now repaired the omission, by presenting above more correct 

 diagnoses. Believing our shell to be the true Turbo Sand- 

 vicensis, I of course adopt, as a matter of right and justice, 

 Mr. Walker's specific appellation. I think no other shell will 

 ever be found to represent Mr. Walker's object. 



Since the above was written, we have had the good fortune 

 to capture several lively animals. 



Animal inhabiting a white spirally striated subglobose shell 

 of four volutions, with a reflexed apex and strong fold on the 

 pillar. The colour throughout is hyaline pale azure. Mantle 

 even with the apertural margin, except a slight canaliculation 

 at the upper angle of the right side. The rostrum, which 

 some call the mentum, is of the exact characteristic essential 

 shape of the tribe ; in quietude it scarcely extends to the ante- 

 rior margin of the foot, but on the march it considerably pre- 

 cedes that organ. The tentacula are proportionately longer 

 than in its congeners, not so triangular, nor furnished with 

 such broad lateral membranes, nor do they coalesce so de- 

 cidedly as in some species to form a veil ; nevertheless they 

 are bevelled and subtriangular, with the eyes at the internal 

 bases. The tip of each tentaculum has a point of flake-white, 

 giving, I think, only the appearance of a slight inflation ; or it 

 may be real for a limited period, caused by the contraction of 

 the muscle of the tentaculum. 



The foot is a singular deviation from that organ in the 

 typical species ; it is short, broad and blunt, truncate ante- 

 riorly, there often twisting itself into acute angles, which, 

 when they happen to fall in a line with the true tentacula, 

 give the appearance of a pair on each side, but a change of 

 position instantly makes that appearance disappear ; the ante- 

 rior third portion of the foot is somewhat contracted ; at this 

 point a transverse groove appears, from the centre of which 

 another longitudinal one proceeds to the posterior end, dividing 

 the foot below the transverse portion into two suboval lobes, 

 each rounded at its termination and separated by an emargi- 

 nation : whether these grooves are only depressions or solu- 

 tions of continuity, I could not in so minute a creature satis- 



