NO. 1205. SYNOPSIS OF THE NAIADES— SIMPSOy. 853 



denticles; one lateral and sometimes a faint secondary one in the left 

 valve and two in the right; dorsal scars few, diversified in form, and 

 variously disposed ia the shallow beak cavities; anterior muscle sears 

 united; nacre whitish. 

 Animal unknown. 



fCTENODESMA BORNEENSIS Issel. 



""Unio lAicatuhis Lea,i Pr. Ac. Kat. Sci. Phila., Ill, 1859, p. 152; Jl. Ac. Nat. Sci. 



Phila., IV, 1860, p. 247, pi. xxxvii, fig. 126; ^Obs., VII, 1860, p. 65, pi. 



XXXVII, fig. 126.—* Reeve, Conch. Icon., XVI, 1865, pi. xxii, tig. 102.— 



*P/ETEL, ConcL. Sam., Ill, 1890, p. 163. 

 ^Margaron (Unio) plicafuliis Lea, Syii., 1870, p. 31. 

 ^Unio horneensis Issel, Moll. Borneo, 1874, p. 113. 

 * Unio 2)enisatiis Fischer and Crosse,- Miss. Sci., Pt. 7, II, 1894, p. 599. 



Borneo. 



tCTENODESMA GUPPYI Smith. 



^Unio (juppyi Smith, Pr. Zool. Soc. Lond., 1885, p. 608, pi. xxxvii, figs. 88a., 

 88?).- "P.etel, Conch. Sam,, III, 1890, p. 154. 



Shortland Island; Solomon Islands. 



Genus RECTIDENS Simpson, 1900. 

 (Type, Unio pj-olongatus Drouet.) 



Shell elongated, with an angle at the anterior dorsal part, pointed 

 and slightly biangulate behind, moderately solid, with two or three 

 posterior ridges, the lower the higher ; beaks full, sculpture not observed 

 but probably zigzag radial ; the posterior slope, and often part of the 

 disk, covered with faint, granular radiating sculpture; epidermis smooth, 

 olive; one compressed, short, recurved pseudocardinal in the left valve 

 under the beak, with a very long one in front of it, and two laterals; two 

 compressed pseudocardinals in the right valve, and a single lateral; all 

 the teeth straight or nearly so; anterior muscle scars separate; beak 

 cavities rather shallow; only one or two dorsal scars in each valve; 

 nacre white or reddish. 



Animal unknown. 



tRECTIDENS SUMATRENSIS Dunker. 



*Unio siimatrensis Dunker, Zeits. fur Mai., IX, 18.52, p. 52. — * Pfeifeer, Nov. 

 Conch., II, 1866, p. 152, pi. xxxix, figs. 10-12.—* vox Martens, Mai. BL, XIV, 

 1866, p. 15.—* P.ETEL, Conch. Sam., Ill, 1890, p. 169. 



Lake Dana I nar, Sumatra. 



'Lea's name was iireoccupied by Kuster, or Charpentier, for a Mexican species in. 

 1856. The name proposed by Issel in 1874 will have to be nsed. 



^Proposed by Fischer and Crosse, because Lea's name jiUcatulus ^vaa preoccuj)ied 

 by Kuster. 



