NO. 1205. SYNOPSIS OF THE XAIADESSIUPSOy. 859 



tTRAPEZOIDENS MISELLUS Morelet. 



* Unio misellus MORELET, Jl. de Condi., XIII, 1865, p. 21 ; * Ser. Conch., IV, 1875, p. 



341, pi. xiv, fig. 2. *P,TEL, Conch. Sam., Ill, 1890, p. 159. 



* t Unio siamensis LEA, Pr. Ac. N. Sci. Phila., X, 1866, p. 133 ; * Jl. Ac. N. Sci. Phila.,' 



VI, 1868, p. 279, pi. xxxvin, fig. 93 ; * Obs., XII, 1869, p. 39, pi. xxxvm, fig. 93. 



* Margaron (Unio) siamensis LEA, Syn., 1870, p. 57. 



TRAPEZOIDEUS PALLEGOIXI Sowerby. 



* Anodon pallegoixi SOWERBY, > Conch. Icon., XVII, 1867. pi. xvn, fig. 17. 

 *Anodonta paUegoui CLESSIN, Couch. Cab. Ano., 1876, p. 210, pi. LXIV, fig. 6. 

 *P.ETEL, Conch. Sam., Ill, 1890, p. 183. 



Siani; Cambodia. 



TRAPEZOIDEUS PENINSULARIS Simpson. 



*Unio sumatrensis SOWERBY, 2 Conch. Icon., XVI, 1865, pi. xxvin, fig. 142. 

 Sumatra. 



TRAPEZOIDEUS EXOLESCENS Gould. ^ 



*Unio exolescens GOULD, Pr. Boat. S. N. Hist., I, 1843, p. 141. *CATLOW and 

 REEVE, Conch. Nom., 1845, p. 59. *H. and A. ADAMS, Gen. Rec. Moll., IF, 

 1857, p. 493. *HANLEY and THEOBALD, Conch. Ind., 1876, p. 43, pi. cvn, 

 fig. 5. *P.ETEL, Conch. Sam., Ill, 1890, p. 152. 



*Margaron ( Unio) esolescens LEA, Syn., 1852, p. 32; 1870, p. 51. 



Tavoy, Burma. 



TRAPEZOIDEUS THECA Benson. 



*Unio theca BENSON, Ann. and Mag., X, 1862, p. 186. *HANLEY and THEOBALD, 

 Conch. Ind., 1876, p. 6, pi. xn, fig. 5. * P.ETEL, Couch. Sam., Ill, 1890, p. 169. 



Cane Kiver, Bundelkhund, India. 



Genus ARCONAIA Conrad, 1865. 

 (Type, Triqueira lanceolata Lea.) 



* Arconaia CONRAD, Am. Jl. Conch , 1, 1865, p. 234. 



Shell greatly elongated, inflated, solid, twisted on its axis, sometimes 

 straight, but generally having the posterior end curved strongly to the 

 right or left, with a decided posterior ridge on both sides of the shell, 

 ending in a blunt point, with usually a small ridge above on the post 

 slope; beaks rather low, sculpture not seen, but probably zigzag radial; 



1 Sowerby says nothing about teeth in his shell, which is from Siaui. The teeth of 

 Lea's specimen of U. siamensis are Scarcely developed, and a comparison of hi shell 

 with Sowerby's figure convinces me that they are very nearly allied. Lea's figure 

 shows the shell biangulate l:ehind, which is an error. 



2 This is not Lea's sumutreiisis, nor that of Dunker. I have therefore changed the 

 name to peninsular h. I am not certain as to its relations. It is not U. comptus 

 Deshayes and Jullien, as Fischer believes 



3 Gould did not figure this, and I have not seen the type. The shell figured as this 

 by Hauley and Theobald in the Conchologia probably belongs here. 



