PULMONATA. 73 
Size-—The specimens ordinarily found rarely exceed 25 inches in length by 
9-10ths of an inch in diameter; one specimen, however, in my collection is above 
3 inches long, and rather more than 1 inch and 2-10ths in diameter; and the 
shell from which fig. 2¢ is taken, forming part of the valuable collection of the late 
Mr. Dixon now in the British Museum, must have exceeded even those dimensions. 
Localities. —Shalcombe, Binstead, Sconce, in the Isle of Wight. 
No. 24. BULIMUS POLITUS. : . Tab. XI, fig. 1 a—d. 
B. testa conicd, levissima, polita ; apice decidue ; anfractibus sub-conveais ; apertura 
ob-ovali, anticé effusd, postice sub-angulatd, peristomate incrassato, reflexo. 
The occurrence of this shell in the fuvio-marine deposit in Headon Hill in such 
abundance as almost to be inconsistent with the supposition that it is a land shell, 
suggests that it might be placed with those Paludinz, in which the margins of the 
aperture are thickened or reflected, and of which an instance (Paludina Chastellii, 
Nyst,) occurs in a similar formation in Hampstead Cliff. The aperture, however, 
and the smoothness of the surface, place it, perhaps, more correctly in the present 
genus, although the latter character is frequently shown in well-preserved specimens 
of Paludina found in a somewhat similar matrix. 
The shell is conical, with a smooth polished surface, on which faint lines of growth 
are barely perceptible; the apex is subject to decollation, leaving about four convex 
whorls ; the last of which, somewhat like that of Nematura, is slightly contracted near 
the aperture, which is rounded and very effuse in front, and angulated behind; the 
peristome is thickened and reflected. The length of the aperture is about 2-5ths of 
that of the whole shell. 
The specific name is one by which the shell is generally known. I do not know 
by whom it was imposed, but it well describes the smooth and polished appearance of 
the shell, and I have therefore retained it. 
Size.—Elevation 2-10ths of an inch; Diameter 1-10th in. 
Locality—Headon Hill. 
Genus 8th. AcHATINA.* Lamarck. 
Cocuuttoma, Férussac. 
Gen. Char.—Shell oval or oblong, subturreted, with an elevated spire; generally 
smooth, but sometimes longitudinally striated: aperture oval or pyriform, generally 
greater in length than in width; outer lip thin, never thickened or reflected ; columella 
* Etym., Diminutive of Aya@os, beautiful; or of Ayarns, an agate. 
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