204 Mr. W. Clark on some of the Animals of the Chemnitziaef. 



or lattice-work on the base, between the ribs, of the three lower 

 volutions. The general colour of the animal, as regards the por- 

 tion contained in the body whorl, is a frosted rather opake white. 

 The mantle is even with the shell, scarcely showing a fold at the 

 upper angle of the aperture. The rostrum is very slender, not 

 cloven, but truncate at the end, and as usual on the march pre- 

 cedes the foot. The tentacula are rather long, slender, not par- 

 ticularly divergent, and have but narrow margins for the auri- 

 form folds j they are taper, bevelled, and terminate in prominent 

 white tips ; the eyes are not very close together at the internal 

 bases. Foot short, narrowish, rarely extending when fully de- 

 ployed much beyond the body volution, truncate in front or 

 very little concave, with short auricles, and a little contracted 

 below them, carrying on a simple upper lobe, at the junction of 

 the foot with the body, a thin, pear-shaped, light, corneous, ob- 

 liquely striated operculum ; the foot has a rather obtuse though 

 lanceolate termination. 



I have reproduced this species, already described by me in the 

 * Annals,' partly with the view of correcting some slight errors, 

 but principally to place it in immediate view for comparison with 

 its tumid variety, and with the next species, the Chemnitzia in- 

 distincta, and its variety that has been named Ch. clathrata, all 

 of which have been strangely jumbled together ; but very large 

 series of both species and their varieties have, I think, enabled 

 me to unravel various misapprehensions. "With respect to the 

 shell of the present species, it has only one well-marked tumid 

 variety, which, as regards the animal, differs in no respect from 

 its chief, as the posterior volutions of both, in the shell, are of a 

 dark lead-colour ; but the variety is invariably of larger size ; 

 the whorls, though the same in number, are more tumid, and 

 the body volution is more than half the whole length of the 

 shell j there is rarely on the body and next turn more than one 

 well-pronounced row of crenje, and a tooth is always visible in 

 the aperture. I have a fine series of more than twenty examples 

 of the variety, and 100 of the type, all of which have been exa- 

 mined alive. 



It is difficult to say whether Montagu's figure represents the 

 shell with the flat or tumid volutions, but as far as the indiffer- 

 ent engraving will allow one to judge, I should guess it to be the 

 tumid variety. I believe, however, all collectors consider the 

 flatter shell the type, it being by far the most abundant. As I 

 find the animals of both absolutely identical, I cannot hesitate 

 to consider the differences of figure as of mere varietal value. 

 The true Ch. interstincta has usually a fold in the aperture, but 

 it is not uncommon without it, and these exceptions are mul- 

 tiplied in most collections by an admixture of some half-grown 



