HYRIA. 



Lam. Hist, Nat. des Aiiim. sans vert. VI. pt. 1. p. 81. 



TESTA sequivalvis, insfequilatera, transversa, 

 obliqufe subtrigona, utrinque auriculata, basi 

 truncata, recta; epidermide olivaeea induta. 

 Impressiones muscular es dusd, postieacomposita. 

 Cardo dentibus duobus elongatis ; dens posticus 

 seu cardinalisj multipartitus, parte externa mar 

 jore lamellari, partibus internis minoribus; ati^ 

 ticus seu lateralis^ lamellaris, prselongus, in 

 altera valva bipartitus. Ligamentum exter- 

 num lineare. 



We have adopted Lamarck's Genus Hyria, because, 

 though we find upon examination, that it possesses many 

 characters in common with Unio, yet we think the two 

 genera are sufficiently distinguished by the elongated 

 lamellar posterior teeth and the two wings of Hyria. 

 Their general form, however, cannot be considered as a 

 good distinguishing character, for we are acquainted 

 both with Anodontes and Uniones, which approach the 

 Hyria very nearly in that particular. These are fresh 

 water shells whose habits approach very nearly to each 

 other, and which form a very natural family with Anodon, 

 Iridina, and Galatea of Lamarck, (Potamophila of our 

 work, and Megadesma* of Bowdich^) and this latter Genus 



* We imagine this name must ]be adopted, because both Galatea and Potamo- 

 phila were previously occupied. 



