PULMONATA. 73 



Size. — The specimens ordinarily found rarely exceed 1\ 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 c 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, lavissimd, politd ; apice deciduo ; anfractibus sub-convexis ; aperturd 

 ob-ovali, antice effusd, postice sub- awgulatd, peristomate incrassato, rejlexo. 



The occurrence of this shell in the fluvio-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 Paludinae, in which the margins of the 

 aperture are thickened or reflected, and of which an instance {Paludina CJiastellii, 

 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 l-10th in. 



Locality. — Headon Hill. 



Genus 8th. Achatina.* Lamarck. 



CoCHLlTOMA, Ferussac. 



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 Ayudos, beautiful ; or of A^arr/i, an agate. 



•10 



