PSEUDODON 1079 



Genus PSEUDODON Gould, 1844. 



Pscudodon Gould, Pr. Bost. Soc. Nat. His., 1844, p. 161. 

 Monodontina Conrad, Pr. Ac. N. Sci. Phila., 1853, P- 269. 

 Trigonodon Conrad, Am. Jl. Conch., I, 1865, p. 233. 

 Monocondylus Morki,f,t, Rev. et Mag., 1866, p. 167. 

 Pseudodiis dk Morgan, Bull. Soc. Zool. Fr., X, 1885, p. 422. 



Shell oval to elongate, having two posterior ridges and often 

 one or two slight, radiating elevations above on the posterior 

 slope, above which there is usually a small wing ; beaks rather 

 low, sculpture unknown : epidermis dark, often having a few 

 faint wrinkles on the posterior slope, without rays when adult. 

 There is a single, smooth tooth in each valve, with occasional 

 vestiges of a second ; laterals nearly or quite wanting ; beak 

 cavities shallow ; dorsal scars conspicuous, deep, distinct, 4 

 to 7 in a row under the hinge ; anterior scars irregular ; nacre 

 generally dull and lurid. 



Animal having the branchiae wide and rounded behind, be- 

 coming narrow in front ; palpi enormously long, apparently 

 slender, pointed behind, where they project free for some dis- 

 tance ; mantle thin, with a wide, slightly thickened border, 

 faintly papillose behind, there seeming to be but little dis- 

 tinction between anal and branchial openings ; anal opening 

 apparently smooth. 



Type, Anodon inoscularis Gould. 



The genus Pseudodon of Gould, as T have defined it, con- 

 tains a limited number of species of Unionidre belonging ex- 

 clusively to the Oriental Region. The shells vary a good deal 

 in form, from nearly orbicular to considerably elongated ; they 

 are generally brownish or blackish and without rays, and with- 

 out striking sculpture. They have usually but a single blunt 

 tooth in each valve, which is almost always smooth. In two or 

 three species there is a vestigial second tooth. The laterals 

 are nearly or quite wanting ; when present they are represented 

 merely by a low, longitudinal ridge. The ligamental patch 

 is mostly rather conspicuous and there is in a number of the 

 forms, a slight indication of a pallial sinus. 



