NO. 1205. STXOPSIS OF THE XATADESSTUPSOX. 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 in the shallow beak cavities; anterior muscle scars 

 united; nacre whitish. 

 Animal unknown. 



fCTENODESMA BORNEENSIS Issel. 



*nno plicatuhtg LEA,' Pr. Ac. Nat. Sci. Phila., Ill, 1859, i>. 152; Jl. Ac. Nat. Sci. 



Phila., IV, 1860, p. 247, pi. xxxvn, rtg. 126; *Obs., VII, 1860, p. 65, pi. 



xxxvn, fig. 126. * REEVE, Conch. Icon., XVI, 1865, pi. xxn, fig. 102. 



* P.KTEL, Conch. Sam., Ill, 1890, p. 163. 

 *Margaron ( Unio) plicatulus LEA, Syn., 1870, p. 31. 

 *Unio borneensis ISSEL, Moll. Borneo, 1874, P- H3. 

 *Unio penisatus FISCHER and CROSSED Miss. Sci., Pt. 7, II, 1894, p. 599. 



Borneo. 



tCTENODESMA GUPPYI Smith. 



*nu'o guppyi SMITH, Pr. Zool. Soc. Lond., 1885, p. 608, pi. xxxvn, tigs. 88a, 

 886. *P.ETEL, Conch. Sam., Ill, 1890, p. 154. 



Shortland Island; Solomon Islands. 



Genus RECTIDENS Simpson, 19OO. 

 (Type, Unio prolongatiis 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 pseudocardiual 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. 



t RECTIDENS SUMATRENSIS Dunker. 



* Unio sumatrengis DUNKER, Zeits. fiir Mai., IX, 1852, p. 52. * PFEIFFER, 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 uar, Sumatra. 



'Lea's name was preoccupied by Knster, or Charpentier, for a Mexican species in 

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



2 Proposed by Fischer aud Crosse, because Lea's name^Zica<Zs was preoccupied 

 by Kuster. 



