Thick Anodon, or Horse Mussel.
Generic Character.—See Pl. 96.
- A. testâ ovatâ, latâ, crassa; margine cardinali subarcuato, extremitate utrâque angulatâ alatâ; umbonibus prominentibus, apicibus retusis.
- Shell oval, broad, thick; hinge margin subarcuated, the extremities winged and angulated; umbones prominent, the tips retuse.
It is only recently that travellers have directed their attention to the less attractive shells of distant regions; and our cabinets now begin to be enriched by the numerous land and fresh-water species of those countries. Among these new acquisitions, the fresh-water bivalves appear the most extraordinary in their formation, and the most numerous in species. Of the Anodons, it may be doubted whether the great Linnæus was acquainted with more than three or four species; Lamarck enumerates fifteen, but a much greater number have passed under my own examination.
The species now illustrated is very peculiar; it is a strong, thick shell; in form resembling Hyria corrugata, Lamarck; having both extremities winged and compressed; the umbonial slope elevated, and somewhat angulated; the umbones thick and prominent, but obtuse, or nearly truncate, at their apex; the outside of the shell of a dark grass-green colour, and nearly smooth, excepting at the posterior side, which is marked by sulcated striæ following the lines of growth; the inside is opaque and whitish, with rich iridescent margins: the muscular impressions deep, and the hinge margin quite smooth.
I know of no other specimen than one in Mr. Dubois' collection, and am altogether unacquainted with its locality; although its habit leads me to think it is from South America.