428 PYRAMIDELLID. 
consider the flatter shell the type, it beg 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 C. interstincta has usually a 
fold in the aperture, but it is not uncommon without it, and 
these exceptions are multiplied in most collections by an 
admixture of some half-grown typical indistincta and the 
variety ‘ clathrata,” which are invariably without the tooth ; 
it never exceeds 52 volutions. 
The type is very common in the coralline district, but the 
tumid variety is oftener met with in shelly mud. 
Cu. inpistincta, Mont. 
Ch. indistincta, Brit. Moll. ii. p. 255, pl. 94. f. 2, 3; and iv. pp. 274, 
277, 278. 
Ch. clathrata, Brit. Moll. i. p. 258, pl. 94. f. 4; and iv. pp. 274, 277. 
The animal inhabits a white sub-opake shell of six or seven, 
sometimes eight, rounded volutions, with close-set waved 
longitudinal plicee that have 3-5 rows of short lines forming 
a lattice-work between the ribs, sometimes upon them at the 
bases of the last three or four whorls; the body is not nearly 
half the length of the entire shell; the aperture is always 
destitute of a tooth. The animal im the body-volution is pale 
yellowish subhyaline white, aspersed with minute snow flakes, 
but the posterior volutions are dark lead-colour, visible 
through the shell. When the neck is greatly protruded, two 
parallel longitudmal Imes are seen, forming an open canal, 
perhaps for branchial purposes. The rostrum is long, rather 
narrow, and just rounded at the termination. The tentacula 
are very short, united at the bases, with their thin margins 
unfurled on the march, which gives them, instead of the usual 
auriform figure, a very large, subtriangular, broad, leafy 
aspect ; they terminate in large inflated white tips, and are 
often delicately powdered with a pale, thin, cloud-like suffu- 
sion of excessively minute lemon-coloured points ; the eyes 
are very black, distinct, and close together at the internal 
bases. The foot is large, thin, subhyaline, either truncate or 
concave in front, dependent on the will of the animal, with 
