I 090 PSKUDODON 



cate ; base line arcuate, fullest behind the middle; anterior end 

 rounded, narrowed ; posterior ridge widely double, ending in 

 a biangulation at and below the median line; surface often hav- 

 ing subvertical folds, also radial plications on the dorsal slope 

 but these are sometimes nearly or quite obsolete in adult 

 shells ; epidermis brownish or coppery, with metallic tints on 

 the disk, subshining ; teeth single in each valve, small, smooth ; 

 dorsal scars deep ; muscle scars shallow but distinct ; nacre 

 livid, copper}^, purplish or salmon-tinted, slightly iridescent. 



Length 65-70, height 38-40, diam. 18-20 mm. 



Borneo. 

 Pseudodon ccneolus Drouet, Jl. de Coiich., XL, 1892, p. 94. — 



Drouet and Chafer, Mem. Soc. Zool. de Fr., V, 1892, p. 



152, pi. VI, figs. 4-7. — Simpson, Syn., 1900, p. 837. 



Very close to P. vondemhuschianiis , but more solid and more 

 coppery-colored. The plications do not seem to be constant. 



Pseudodon resupinatus von Martens. 



"Shell oblong, moderately thick, quite compressed, sculp- 

 tured on the posterior and upper parts with radiating folds, 

 curved and ascending towards the margin and more or less 

 subdivided, elsewhere smooth ; epidermis black, somewhat 

 shining ; anterior margin rounded ; posterior dorsal margin 

 curved as far as the sinulus, thence oblique and straight ; 

 posterior end sub-biangulate, quite short, perpendicular; ven- 

 tral margin straight, in old shells slightly sinuate ; cardinal 

 teeth single in both valves, thick, obtuse ; posterior cardinal 

 somewhat thick, obtuse ; sinulus inequilateral, low, obtuse- 

 angled ; nacre bluish-pearly ; anterior muscular iniijDressions 

 deep, posterior superficial, anterior accessory impression quite 

 deep. 



Length 73, height, vertical 2,2. alse 38, diam. 22 mm. Beaks 

 situated at 1/5 of the length." (von Martens). 



Type locality. Than-Hoi, Tonkin. 

 Pseudodon resupinatus von ^L\rtens, Nachr. Deutsch. Mai. 



Ges.. 1902, p. 131. 



