Natica. MOLLUSCA. PECTINIBRANCHIA. 319 
G. '^.costafa. Hemispherical; spire conspicuous, impressed; whorls trans- 
versely costated ; costse thin, sharp, numerous ; aperture expanded, orbicu- 
lar ; columellar lip prominent, obtuse. Sower. Min. Conch, t. cccclxiii. f. 5, 
G. Oolite, AnclifF. 
7 . N. spirata. Semiglobose, smooth ; spire small, partly immersed ; upper 
parts of the whorls flat, when old, concave ; aperture transversely oval 
Sower. Min. Conch, t. cccclxiii. f. I, 2. Mountain Limestone. 
8. N. — I possess some imperfect specimens of a species differing 
from the preceding in size, and in the spire being larger. From the Tran- 
sition Limestone of Cork. 
9. N. striata. Spire slightly produced ; whorls flat, crossed by numerous 
nai'row rounded ribs. I found an imperfect specimen of this shell in Carboni- 
ferous Limestone qX, Corry,IArran 5th June I 8 O 7 . It bears a close resemblance 
to the recent Nerita polita. 
Gen. LVIII. NATICA.— Pillar-lip entire, not entering the 
aperture, with a cavity or callus behind. 
27s. N. Whorls six, smooth, pillar-iip thick and 
reflected, forming a large and deep cavity. 
Cochlea rufescens, List. An. Ang. 163. t. iii. f. 10. Conch. 568. f. |19. — 
Nerita glaucina, Linn. Syst. i. 1251. Mont. Test. Brit. 469. Inhabits 
deep sandy bays, common. 
Length about an inch and a half, breadth rather less ; whorls little elevat- 
ed ; apex pointed ; colour brownish white, with interrupted bands of brown 
on the upper volutions ; outer lip considerably advanced at its junction with 
the body ; operculum divergingly striated. Mr Hog has demonstrated, that 
the substance known under the name of Flustra arenosa, is the nidus of this 
species, in the cells of which the eggs are deposited. Linn. Trans, xiv. 318. 
The Nerita pellucida and alba of Adams, ib. iii. 67. are probably the fry of 
this species. 
273. N. nitida. — Whorls five ; pillar cavity half closed. 
Nerita nit. Don. Brit. Shells, 144. Mont. Test. Brit. Sup. 149. On 
different parts of the coast, not common. 
Diameter scarcely half an inch ; glossy, white ; spire short ; whorls nearly 
flat, with the separating line nearly obliterated. 
274. N. Smooth, purplish, with a white band round 
the top of the volutions, and two others on the body-whorl. 
Nerita rufa, Mont. Test. Brit. Sup. 150. t. xxx. f. 3. English and Scot- 
tish coast, rare. 
Breadth about half an inch ; pillar-lip forms a large projection over the ca- 
vity behind, producing an indenture on each side of it. The second whorl 
in this is larger in proportion than in N. glaucina. 
275. N. Pillar-cavity furnished with two spiral 
ridges and two grooves. 
Nerita in. Don. Brit. Shells, t. clxvii. N. canrena, Mont. Test. Brit. 
Sup. 148. Weymouth, rare. 
Length about half an inch ; smooth, livid, with bands of sagittate ferrugi- 
