NO. 1205. SYNOPSIS OF THE NAIADES SIMPSON. 839 



Section BINEURTJS 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, Monooondglaa moultoti Lea.) 

 tPSEUDODON MOUHOTI Lea. 



* Monocondylna moulioti LEA, Pr. Ac. N. Sci. Phila., VII, 1863, p. 190. 



* Pseudodon manlioti CONRAD, Am. Jl. Conch., I, 1865, p. 233. 



* Monocondylaa mouhotiana LEA, Jl. Ac. N. Sci. Phila., VI, 1866, p. 65, pi. 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,ETEL, Conch. Sam., Ill, 1890, p. 175. 



* Maryaron (monocondylaa) moulioiiana LEA, Syn., 1870, p. 73. 



* Unlo mouhotianus SOWERBY, Conch. Icon., XVI, 18(58, pi. xcn, fig. 503. 



* Pseitdodon mouhotianus MORELET, Ser. Conch., IV, 1875, p. 339. 



Cambodia; Siam. 



PSEUDODON EXILIS Morelet. 



* Monocondylus exilis MORKLET, Jl. de Conch., XIV, 1866, p. 63. 



* Psexdodon exilis MORELET, Ser. Conch., IV, 1875, p. 340, pi. xvn, fig. 1. 



Perak. 



PSEUDODON AVA Theobald. 



* Monocondyloca ava THEOBALD, Jl. A8. Soc. Beng., XLII, Pt. 2, 1873, p. 209, pi. 



xvii, fig. 15.' 



Mandelay, Burma. 



Section NASTJS Simpson, 1900. 

 (Type, Pseudodon nankingensis Heude.) 



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. 2 



Animal unknown. 



fPSEUDODON NANKINGENSIS Heude. 



* Monocondyloca nankingensis HEUDE, Jl. de Conch., XXII, 1874, p. 116; Conch. 



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



* Monocondyla'a itankinyensis P.ETEL, Conch. Sam., Ill, 1890, p. 174. 



Eivers of Nankin. 



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



2 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 accurately. The 

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



