IRIDINA. 



Ltam, — Hist. Nat. des Anim. sans vert. vi. p. 89. 



^ »■ ■ 



TESTA aequivalvis^ inaeqiiilatera^ transversa, um- 

 bonibus parvis, subrecte infiexis. Cardo elon- 

 gatus, linearis^ versus medium attenuatus^ per 

 longitudinem tuberculosus^ subcrenatus^ tuber- 

 culis inaBqualibus, crebris. Impressiones muscu- 

 lar es treSj irregulares^ laterales, duas posticfe; 

 tertia magna^ antica^ remota. Ligamentum exter- 

 num^ marginale. 



The only species of this Genus at present known was ar- 

 ranged by Bruguiere among his Anodontites {Anodon^ 

 Swainson), and it is certainly so nearly related to them, 

 that Lamarck thought Bruguiere might be authorized in 

 uniting- it to them : nevertheless its hinge line, tubercular 

 throughout its length, is in that respect so singular, that 

 Lamarck has made it the type of a particular Genus. 



Shell equivalve, inequilateral, transverse ; umbones 

 scarcely distinct, but nearly straight. Hinge margin^ 

 long, linear, attenuated towards the umbones, consisting of 

 subcrenated, unequal, small, close-set tubercles throughout 

 its length. Muscular impressions three, lateral, irregular, 

 two of them placed at the posterior side, one of these being 

 much smaller than the other, and anterior to it ; the third, 

 large, placed at the opposite or anterior side of the shell. 

 Ligament external, long, marginal. 



According to Lamarck, the Iridina elongata is found 

 in the rivers of warm climates ; it is a transversely oblong 



* A term adopted from Swainson. 



