GASTEROPODA. 249 
volving threads, becoming larger as they approach the base. Whorls 
twelve, having a delicate raised line bordering the suture, followed by 
a concavely excavated canal, then a series of oblique, tubercular folds 
at the middle not reaching the suture below: aperture one-third the 
length of the shell, narrow: rostrum short, slightly recurved; notch 
about as deep as broad, opposed to a conspicuous callus on the left lip ; 
pillar nearly straight, pale purplish-brown; interior livid. 
Length an inch and three-eighths ; breadth three-eighths of an inch. 
Habitat unknown; obtained by Lieut. Walker. 
Closely allied to P. tnterrupta, Lamarck, but differing from the 
figures in colour, and from the description in having a more decidedly 
excavated girdle in front of the suture, in the greater obliquity of the 
folds, and in their not reaching to the suture below. 
Figures 312, 312 a, two views of the shell. 
PLevROTOMA TIGRINA (LAmaRck), Anim. sans Vert., ix. 352. KIENER; 
Iconog., pl. 8, f. 1. Reeve; Conch. Icon., f. 3. 
Foot oval, the anterior angles dilated; beneath violaceous, mottled 
with small, deep violet spots; above pale, with scattered lilac and 
orange mottlings. Operculum not near the tip of the foot. The 
rostrum is conical and cleft vertically at the end; the tentacles are 
small, subulate, coming off behind the termination of the snout, 
and having the eyes at the distal third, without a distinct pedicle. 
Motions moderate. 
Habitat, Upolu, Samoa Islands. Drayton. 
Quoy gives the animal of P. Babylonica, as having the eyes at the 
outer base of the tentacles, and the rostrum as abrupt and cleft below. 
The description was probably made out from a contracted specimen. 
Figure 311, the animal as in crawling; 311, the locomotive disk. 
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