A treatise on malocology, or the natural classification of shells and shell-fish / By William Swainson.

  • William Swainson
Date:
1840
Catalogue details

Licence: Public Domain Mark

Credit: A treatise on malocology, or the natural classification of shells and shell-fish / By William Swainson. Source: Wellcome Collection.

    189/440 (page 175)
    families, before the whole tribe has undergone a careful examination. (l63.) The foregoing series, constituting the sec- tional types of our sub-genus Achatina, will be ren- dered more plain to the general reader, if thrown into a table in the following manner: — Analogies of the Species in the Sub-genus Aciiatina. Sectional Sub-genera Genera Division of Analogical Characters. of of the the Species. Aciiatina. Aciiatinjj. A. Zebra. A. clongata. A. perversa. A. Sultana. A. virginea. Achatina. Cochlicopa. Bulimus. ^ Ovate; ventricose; spires short; outer lip simple, > Achatina. not sinuated. J (Ovate; aperture nearly or quite entire ; spire more lengthened. J l 1Macrospira- 1 [SP]reeep?ytneoJch°eS:eSSed! ^ j ^ AcAatine/la. Cvclostoma. f Aperture nearly round; 1 margined. Now, this is the smallest group which can be made out, next to the actual species which come under each section ; and yet every conchologist who possesses an extensive series of these shells, or even of those we have named, must perceive that no other divisions, or sec- tions, can be formed with any degree of propriety ; that is to say, if he were asked to single out the most diver- sified forms from the sub-genus Achatina, the above are those he would probably fix upon. Now, this series, small as it is, turns out to have a circular succession ; and not only that, but likewise to represent all the sub-genera and genera of the family. Hence it would seem that the essential character of this sub-genus is to have the contour of the aperture simple — not sinuated or dilated, as in the next sub-genus, Cochlicopa. The Cochlicopa maculata thus seems to be neither an Achatina, nor a distinct sub-genus, as some have imagined, for we do not believe it is a marine mollusk. (164.) The preceding analysis of Achatina inci-