426 PYEAMIDELLID^E. 



front ; it issues from the tentacular membrane, and is placed 

 between it and the foot, and is of greater length; on the 

 march it is carried in advance of the foot, but the tentacula 

 always reach beyond the rostrum, which only very rarely, by 

 an extraordinary exertion, is extended to the tentacula: I 

 mention this because I have seen the animal figured with the 

 rostrum as long as the tentacula, which is an unusual 

 position. The tentacula occupy the extent of the membrane 

 from which they originate, coalescing at their bases, and 

 diverging greatly to their points ; they are short, flat, broad, 

 bevelled, triangular, blunt, setose, with a snow-white line from 

 base to point, and a round intense flake-white dot at their 

 tips, which give them the aspect of being clavate ; the eyes 

 are large, black, placed on the skin at the internal bases of 

 the tentacular bifurcation, beneath which is the proboscidal 

 orifice. The foot is slightly auricled, and sinuated on each 

 side so as to make a gradual central indentation ; it is rather 

 broad, perfectly round posteally at half extension, but in full 

 march it tapers to a moderately pointed lanceolate termina- 

 tion, carrying on a plain upper lobe a suboval, light corneous, 

 finely striated, simple operculum. 



The animal is active, and shows its peculiarities sans facon. 

 It inhabits at Exmouth the coralline, laminarian, and the 

 lowest littoral levels. It scarcely differs from C. rissoides, 

 except in being white instead of speckled with yellow, and in 

 the foot being sinuated in front instead of truncate. There 

 is usually a fold on the pillar. 



CH. INTERSTINCTA, Mont. 

 Odostomia interstincta, Brit. Moll. iii. p. 296, pi. 97. f. 1. 



Animal inhabiting a closely plicated white shell of five and 

 a half flattish volutions, the body not being half the length of 

 the shell ; the apex is less reflexed than usual ; the aperture 

 has generally a visible tooth, and there are one or two rows 

 of crense or lattice- work on the base, between the ribs, of the 

 three lower volutions. The general colour of the animal, as 

 regards the portion contained in the body whorl, is a frosted, 



