NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSON. 839 



Section BINEURUS Simpson, 1900. 



Shell elongate rhomboid, thin, rounded in front, widely and feebly 

 biangulate behind, having two or more raised radiating lines on the 

 posterior slope, which is somewhat obliquely wrinkled; beaks low; sur- 

 face finely, irregularly, concentrically grooved; epidermis olive; teeth 

 smooth, compressed; nacre bluish. Animal unknown. 



(Type, Monocondylwa mouhoti Lea.) 

 fPSEUDODON MOUHOTI Lea. 



* Monocondylcm mouhoti Lea, Pr. Ac. N. Sci. Pliila., VII^ 1863, p. 190. 



* Pseiidodon manlwii Conrad, Am. Jl. Concli., I, 1865, -p. 233. 



* Monocondylaca mouhotiana Lea, J]. Ac. N. Sci. Phila., VI, 1866, p. 65, pL xxi, 



fig. 62; ^ Obs., XI, 1867, p. 69, pi. xxi, fig. 62.—^ Clessin, Conch. Cab. Ano., 

 1876, p. 261, pi. Lxxxii, figs. 1, 2.— "P^tel, Conch. Sam., Ill, 1890, p. 175. 

 * Ma7'(jarou (monocondylaa) mouhotiana Lea, Syn., 1870, p. 73. 



* Unto monhoHanus Sowerby, Conch. Icon., XVI, 1868, pi. xcii, fig. 503. 



* Pseiidodon motiliotianus Morelet, Ser. Conch., IV, 1875, p. 339. 



Cambodia; Siam. 



PSEUDODON EXILIS Morelet. 



* Monocondyliis exilis Morelet, Jl. cle Conch., XIV, 1866, }). 63. 



*" Pseiidodon exilis Morelet, Ser. Conch., IV, 1875, p. 340, pi. xvii, fig. 1. 



Perak. 



PSEUDODON AVA Theobald. 



* Monocondylcea ava Theobald, Jl. As. Soo. Beug., XLII, Pt. 2, 1873, p. 209, pi. 



XVII, fig. 15.' 



Mandelay, Burma. 



Section NASTJS Simpson, 1900. 

 (Type, Pseiidodoti nankingensis Jiende.) 



Shell somewhat solid, rather inflated, much elongated, with a well- 

 developed posterior ridge, with a low, faint one above it, bluntly pointed 

 at post-basal part; beaks not high, eroded in the specimens seen; epi- 

 dermis dark; teeth compressed, high.^ 



Animal unknown. 



tPSEUDODON NANKINGENSIS Heude. 



* Monocondylcea nankingensis Heude, Jl. de Conch., XXII, 1874, p. 116; Couch. 



FluY. Nank., I, 1875, pi. iv, fig. 9. 



* Monocondyla'a nankingensis P.etel, Conch. Sam., Ill, 1890, p. 174. 



Elvers of Nankin. 



'I am not certain that this belongs in this group. 



^I have seen only a single shell of each of the two species of this group, both very 

 badly eroded and decayed, so that I can not give the characters accaratelj\ The 

 animals may show that they are not closely related to the ordinary Pseudodons. 



