Zoological Illustrations/VolIII-Pl162

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Zoological Illustrations
by William Swainson
Vol III. Pl. 162. Achatina fasciata (var). Banded Achatina.
Zoological Illustrations Volume III Plate 162.jpg

ACHATINA fasciata, (var.)

Banded Achatina, (3 varieties.)

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Generic Character.—See Pl. 30.

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Specific Character.—See Pl. 74.

(Young.) Aperturâ basi integrâ. Base of the aperture entire.
Ach. pallida. Zool. Ill. vol. 1. pl. 41.
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Since the first illustration of this elegant species appeared, at plate 74 of this work, I have had the means of ascertaining a very extraordinary circumstance which takes place in the progressive growth of the young shell to the adult state; and that is the change effected in the form and termination of the pillar or columella. In the noble collection of shells formed by the late Earl of Tankerville, there is a numerous series of this species; from these I have ascertained, that in the young shells the base of the columella unites with the termination of the outer lip, making the aperture entire, similar to the lengthened Helices; but, as the shell advances in growth, the base of the columella becomes thick, detached, as it were, from the marginal rim, so as to produce an intervening notch, and thus gives the old and the young shell not only an appearance of being distinct species, but of belonging to separate genera. From these facts, I have drawn the conclusion, that Achatina pallida (pl. 41), is but the young shell (having the margin of the aperture as yet entire) of Achatina fasciata; and the three additional varieties now figured, will, I hope, prove an interesting addition to the history of this species.