Il62 RECTIDENS 



Rkctidkns oRinxTAi.is (Lea). 



Shell somewhat elongated, svthelHptical or subrhomhoid, con- 

 vex, inequilateral, scarcely subsolid ; dorsal line nearly straight ; 

 anterior end rounded, full and almost subangulate above ; base 

 line curved, full behind the middle ; dorsal slope obliquely sub- 

 truncate ; beaks scarcely raised ; posterior ridge subangulate, 

 pinched-up above, ending below the median line in a rounded 

 point ; above the posterior ridge there is a low, radial pinched- 

 up ridge ; epidermis nearh^ smooth, showing feeble corrugations 

 at the anterior end and traces of nodules on the disk, yellowish- 

 green with green bands and two green rays on the posterior 

 end, shining ; teeth compressed ; the pseudocardinals showing a 

 tendency to break up into dentilations ; nacre bluish, yellow- 

 tinted in the cavities of the shell. 



Length 2i^, height 16.5, diam. 9 mm. 



Java. 

 Unio orientalis Lua, Pr. Am. Phil. Soc, I, 1840, p. 285 ; Tr. 



Am. Phil. Soc, VIH, 1842, p. 221, pi. xviii, fig. 38; Obs., 



in, 1842, p. 59, pi. XVIII, fig. 38. — Chenu, 111. Conch, 1858, 



pi. XXXII, figs. 6, 6a, 6b. — Kuster, Conch. Cab. Unio, 1861, 



p. 241, pi. Lxxx, fig. 16. — SowERBY, Conch. Icon., XVI, pi. 



xci, fig. 491. 

 Margaron (Unio) orientalis htA, Syn., 1852, p. 38; 1870, p. 61. 

 Nodnlaria orientalis Simpson, Syn., 1900, p. 819. 

 Elongaria orientalis Hy\AS, Con. Cab., Unio, 1910, pi. xvii., 



figs. 3-5- 

 Unio prodiictiis Mousson, L. and S. W. Moll., Java. 1849, P- 



93, pi. XVII, figs. 3-5. 

 Unio productior Lea, Syn. 1852, p. 29. 



Lea's shell, the type of Unio orientalis, is, no doubt, young 

 and it seems to be identical with fig. 5, plate xvii, in Mousson's 

 Land and Susswasser-Mollusken von Java, which he refers to 

 his Unio productus. I am not at all sure that his figure 3 on 

 the same plate represents this species, as it has more the appear- 

 ance of some of the Kuropean forms of the group of Unio 

 pictorum. 



Haas has recently (Nachr. Deutsch. Mai. Ges.. 191 3. p. 34), 

 made this species the tvpe of a new genus, PJoui^aria. 



