588 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxii. 



^Margarita (Anodonia) exilis Lea, Syn., 1838, p. 32. 



* Anodon exilis Catlow aud Reeve, Concli. Nora., 1845, p. 66. 



^ Margaron {Ayiodonta) exilis Lea, Syn., 1852, p. 51; 1870, p. 82. 



■* Monocovdylcea exilis P^etel, Conch. Sam., Ill, 1890, p. 174. 



" Anodonta siliqna Kuster? Conch. Cab. Ano., 1852, p. 57, pi. xiv, hg. 5. 



'' Anodonta jiolita MoussoN, L. and Suss. Moll. Java, 1849, p. 98, pi. xix, figs. 2, 3. — 



*MoussON, Zeits. fur Mai., VII, 1851, p. 46. — *H. and A. Adams, Gen. Rec. 



Moll., II, 1857, p.504.— *P^TEL, Conch. Sam., Ill, 1890, p. 183. 

 ^ Mar gar on {Anodonta) polita Lea, Syn., 1852, p. 53. 



* Anodon politus Sowerby, Conch. Icon., XVII, 1867, pi. xii, fig. 36. 



*" t Monocondylaa comjiressa Lea, Pr. Ac. N. Sci. Phila., VII, 1863, p. 190; * Jl. Ac. 

 N. Sci. Phila., VI, 1866, p. 30, pi. xi, fig. 29; * Ohs., XI, 1867, p. 34, pi. xi, fig. 

 29.—* Clessin, Conch. Cab. Ano., 1876, p. 258, pi. lxxx, figs. 3, 4. 



* Pseudodon compressa Conrad, Am. ,J1. Conch., I, 1865, p. 233. 



* Margaron (Monocondylcea) compressa Lea, Syn., 1870, p. 73. 



* Spatha comprtssa P.etel, Conch. Sam., Ill, 1890, p. 188. 



^ Anodon javan a Sowerby, Conch. Icon., XVII, 1867, pi. xi, fig. 33. 

 " Anodon gracilis Sowerby? Conch. Icon., XVII, 1867, pi. xiv, fig. 45. 



* Anodon keUetti Sowerby? Conch. Icon., XVII, 1867, pi. xix, fig. 71. 



* j Anodonta sempervivens Deshayes, Nouv. Arch, de Mtis., X, 1874, p. 120, pi. v, 



figs. 4, 5.— *PiETEi., Conch. Sam., Ill, 1890, p. 184. 



Southeastern Asia, Sumatra, Java. 



jPILSBRYOCONCHA CARINIFERA Conrad. 



''Anodonta carivifera Conrad, Cover of Mouography, No. 9, 1837. i — Troschel, 

 Arch, fiir Naturg., IV, 1838, Pt. 2, p. 288.— B. H. Wright, Check List, 1888. 



Southeastern Asia, probably. 



PILSBRYOCONCHA LEMSLEYI Morelet. 



"* Anodonta lemsleyi Morelet," Ser. Conch., IV, 1875, p. 328, pi. xiv, fig. 1. — P^tel, 

 Conch. Sam., Ill, 1890, p. 181. 



Cambodia, Siam. 



PILSBRYOCONCHA SCHOMBURGKI von Martens. 



*Anodonta schomburgki von Martens, Proc. Zool. Soc. Loud., I860, p. 15. — 

 "Retel, Conch. Sam., Ill, 1890, p. 184. 



Siam. 



Genus MEDIONIDUS Simpson, 1900. 

 (Type, Unio conradicns Lea.) 

 Medionidus Simpson, Pr. Ac. N. Sci. Phila., 1900, p. 77. 



Shell elong^ated, rather inflated, often arcuate when adult, sometimes 

 having a posterior ridge; dorsal slope and occasionally the posterior 



'There is a specimen of Pilsiryoconcha iu the Philadelphia Academy which agrees 

 perfectly with Conrad's description, and is probably the type. My attention was 

 called to this by Mr. Pilsbry, who believes this to be the shell Conrad described. It 

 is rather a small species. 



-An old, elongated, rather peculiar shell. Conrad's species may be the young of 

 it, and Morelet believes that Martens' A. schombiirgM is very close to his shell I 

 have not seen a sufficient amount of material of this genus to determine with cer- 

 tainty whether all these are valid species. 



