ANODON crassus, 

 Thick Anoclon, or Horse Mussel. 



Generic Character. — See PI. 96. 



Specific Character. 

 A. testd ovatd, laid, crassa ; margine cardinali subarcuato, extremi- 

 tate utrdque angulatd alatd ; 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 atten- 

 tion 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 extra- 

 ordinary in their formation, and the most numerous in 

 species. Of the Anodons, it may be doubted whether the 

 great Linnaeus 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 striai following the lines of 

 growth; the inside is opaque and whitish, with rich iri- 

 descent 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 ; 

 althouo-h its habit leads me to think it is from South America. 



* I have applied this term to the oblique descent made bv the umbo, 

 towards the basal extremity of the anterior side of bivalves. 

 PI. 167, 



