SYNOFSIS OF THE NAIADES— SIMPSON. 587 



and one lateral, which is reflexed upward ; epidermis folded into the 

 hinge, and scaly; a single dorsal scar on the inner side of each hinge 

 plate; muscle scars united ; palleal line distinct; beak cavities large and 

 wide; nacre very dull. Animal unknown. 



tLEPIDODISMA LANGUILATI Heude. 



' Unio languilati Heude, .J. de Conch., XXII, 1874, p. 116; '"Conch. Fluv. Nank., 



I, 1875, pi. VII.— P.ETEL, Conch. Sam., Ill, 1890, p. 156. 



■ Lepidodesma langnilaU Simpson, Pr. U. S. Nat. Mus., X.VIII, 1896, p. 311. 



* Cristaria megadesma von Martenis, S. B. Nat. Fr., 1875, p. 3; * Mai. Bl., XXII, 



1875, p. 187; * Nov. Conch., IV, 1876, p. 152, pi. cxxxv, fig. 1. 



* Barbula megadesma P^tel, Conch. Sam., Ill, 1890, p. 175. 



China. 



LEPIDODESMA ALIGERA Heude. 



* Unio langiiilatus var. aligeriis Heude, Conch. Fluv. Nank., Ill, 1877, pi. xvii, 



fig. 37.— *P.ETEL, Conch. Sam., Ill, 1890, p. 156. 



* Lepidodesma aligera Simpson, Pr. U. S. Nat. Mus., XVIII, 1896, p. 311. 



China. 



Genus PILSBRYOCONCHA Simpson, 1900. 

 (Type, Anodonta exilis Lea.) 



Shell elongated, elliptical, compressed, thin, with a low, posterior 

 wing, narrow and rounded in front, nearly straight below, expanded at 

 the post-basal region, pointed behind. Beaks compressed, sculptured 

 with several coarse, low, irregularly concentric undulations, often 

 slightly doubly looijed; surface nearly smooth, shining, yellowish to 

 ashy brownish, sometimes showing very faint rays; hinge straight or 

 slightly curved, reduced to a mere line, often showing a faint, com- 

 pressed, smooth tooth in front of the beaks, otherwise edentulous; 

 nacre brilliant, silvery and iridescent; muscle scars faint. Animal 

 pure milky white; lobes of the mantle united behind into two short 

 siphons.^ . ' 



t PILSBRYOCONCHA LINGU^FORMIS Morelet. 



^Anodonta ^m</!(ff/o>'m/s Morelet, Ser. Conch., IV, 1875, p. 329, pi. xiv, fig. 5. — ■ 



* P^tel, Conch. Sam., Ill, 1890, p. 181. 

 ^ Mar gar on (Unio) lingua-formis Lea, Syn., 1870, p. 48. 



Siam; Cambodia. 



t PILSBRYOCONCHA EXILIS Lea. 



"" Anodonta exilis Lea, Tr. Am. Phil. Soc, VI, 1839, p. 81, pi. xxii, fig. 68; *Obs., 



II, 1838, p. 81, pi. XXII, fig. 68.—* Troschel, Arch, fur Naturg., V, 1839, Pt. 2, 

 p. 239.— * Hanley, Test. Moll., 1842, p. 224; ^ Biv. Sheils, 1843, p. 224.— 

 " H. and A. Adams, Gen. Rec. Moll., II, 1857, p. 503. — * Morelet, Ser. Conch., 

 IV, 1875, p. 327. — 'Clessin, Conch. Cab. Auo., 1875, p. 171, pi. lvi, figs. 

 6-8.— * P.ETEL, Conch. Sam., Ill, 1890, p. 179. 



'According to Deshayes, ,11. de Couch., 1875, pp. 81-85. He does not give any other 

 characters of the soft parts. 



