3^0 MOLLUSCA. PECTINIBIIANCHIA. Natica. 
nous lines ; pillar-cavity very large. This species has occurred only to Mi‘ 
Donovan. 
276. N. tuber osisshna. — Whorls four, marked with four spi- 
ral broken tubercular ridges. 
Nerita tub. Mont. Test. Brit. Sup. 150. t. xxix. f. 5.— At Dunbar, Mr 
Laskey. 
Breadth about |th of a^i inch; pellucid, white; upper volutions small ; 
pillar-cavity large. 
277. N. sulcata. — Whorls four, with remote oblique trans- 
verse striae. 
Nerita sul. Turton. Conch. Diet. 124. fig. 56, 57.— N. glabrissimus, 
Brown, Wern. Mem. ii. 532. t. xxiv. f. 12. — Two specimens found in 
Dublin Bay by Dr Turton. 
Breadth |th of an inch ; globular, semitransparent, bluish-white ; whorls 
swollen, well defined ; pillar-lip flat, projecting a little in the middle over 
the cavity behind, which is long and deep. 
278. N. pallidula. — Whorls three, pillar-lip with a wide 
groove leading to the cavity. 
Ner. pall. Don. Brit. Sh. t. xvi. f. i. Mont. Test. Brit. 468. — Turbo pal- 
lidus and puteolus, Turt. Conch. 192.— Among sea weeds, about low 
water-mark, common. 
Length ^ an inch, breadth |ths ; yellowish-brown ; whorls rounded, with 
a grooved separating line, the upper ones small, lateral, and little produced, 
slightly wrinkled by the layers of growth ; pillar-cavity deep, the retral ex- 
tremity of the lip partly folded over it ; operculum with diverging wrinkles. 
279. N. lacuna. — Whorls four ; pillar-lip with a narrow 
groove leading to the cavity. 
Ner. lac. Mont. Test. Brit. 428. t. xiii. f. 6 — Turbo lacuna, Turt. Conch. 
Diet. 193. t. XXV. f. 87, 89 — On the English shores, rare. 
This shell bears a very close resemblance to the preceding. Judging from 
an authentic example which I received from Mr Montagu, it chiefly differs 
in the less enlargement of the body-whorl towards the aperture, the second 
whorl being better defined, the pillar-groove narrower, and the anteal cur- 
vature of the lip more restricted : there are likewise some faint traces of spi- 
ral striae. 
EXTINCT SPECIES. 
1. IS^. glauemoides — Nearly globose spire, rather elongated ; pillar-cavity 
simple, partly covered ; upper part of each whorl slightly depressed — Sower. 
jMin. Conch, t. v. three upper figures, and t. cccclxxix. f. 4 — London Clay and 
Suffolk Crag. 
2. N. similis. — Shell rather rhomboidal ; spire short ; pillar cavity divided 
hy a spiral projection ; aperture slightly angular above. — Sower. Min. Conch, 
t. V. two middle figures. — London Clay. 
3. N. depressa — Nearly globose, subumbilicated ; upper part, and the side 
of each whorl, flattened, so as to appear nearly square ; columella depressed 
beneath ; aperture angular at the upper part.— Min. Conch, t. v. lower 
figures. — Crag-marl. 
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