428 PYKAMIDELLIM:. 



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 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 5 volutions. 



The type is very common in the coralline district, but the 

 tumid variety is oftener met with in shelly mud. 



CH. INDISTINCTA, Mont. 



Ch. indistincta, Brit. Moll. iii. p. 255, pi. 94. f. 2, 3 ; and iv. pp. 274, 



277, 278. 

 Ch. clathrata, Brit. Moll. iii. p. 258, pi. 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 plicae 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 in 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 longitudinal lines 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 



