I 148 PTYCIIORHVXCHUS 



Unio sclioiiibiirgiiDius Heude, Conch. Fluv. Xank., IX, 1885, 

 pi. Lxxii, fig-. 139. — Fischer, Jl. de Conch., XL, 1892, p. 314. 

 Ptychorhynchiis sc/ioinbnrgianiis Simpson, Syn., 1900, p. 851. 

 Close to P. aficcUatum, but less decidedly rhomboid and not 

 distinctly biangulate behind. It seems to stand between that 

 species and the varieties of pfisteri. Heude states that the epi- 

 dermis is radiate, but the figure does not show it. 



Ptychorhynciius NrEuwENHUisi (Schepman). 



Shell long, subrhomboid, convex or almost compressed, in- 

 equilateral ; beaks apparently low and subcompressed ; pos- 

 terior ridge low, widely double, ending behind in a wide bian- 

 gulation from a point below the median line to the base ; an- 

 terior end very slightly narrowed, rounded ; base line nearly 

 straight ; dorsal line lightly curved ; dorsal slope obliquely 

 truncate above, the truncation meeting the dorsal line at a 

 low angle and the biangulation below at a sharper angle ; 

 surface apparently concentrically striate, the striation coarser 

 below ; posterior end of the shell covered with rather fine, 

 curved, radiating folds which are slightly divaricate on the 

 upper part of the posterior ridge ; epidermis dark brown, 

 fibrous ; hinge strong ; one thick pseudocardinal in the right 

 valve and two in the left ; one lateral in the right valve 

 and two in the left, lightly curved and crenate posteriorly ; 

 anterior scars deep, irregular ; posterior scars shallow ; pallial 

 line distinct : nacre iridescent, olive-yellow in the cavities, blu- 

 ish-white on the border. A flat callosity runs from the beaks 

 within obliquely towards the ventral margin. 



Length 69, height 40, diam. 19 mm. 



Bloe-oe, East Borneo. 

 Unio nieuwenhuisi Schepman, X^otes Leyd. Mus., XX, 1898, 



p. 92, pi. I, figs. I. 2. — Drouet, Jl. de Conch., xevii, 1899, 



p. 406. 

 Unio nezvenhnisi Simpson, Syn., 1900, p. 803. 

 Schepmania nienavenhuixi Haas. Con. Cab., L'nio, 1910, pi. 



XII, fig. 3. 



