PSKUDODON 1099 



PSEUDODON BICRISTATUS (Strubcll). 



"Shell almost regularly ovate, rather thin, small, scarcely 

 inflated, lightly striate, not very shining, olivaceous-brown. 

 Anterior end short ; posterior end moderately elongated, di- 

 lated, the greatest height being at the postero-dorsal angle. 

 Dorsal margin short, almost straight, ascending, forming a 

 distinct angle posteriorly, an indistinct one in front; anterior 

 end very shortly rounded ; basal margin scarcely curved, 

 slightly ascending posteriorly, forming with the posterior mar- 

 gin a short, biangulated, truncated beak. Umbones anterior, 

 depressed, widely, but superficially, eroded; areola none; area 

 elongate, compressed, distinctly bicarinate, carinae prominent 

 at the posterior margin ; ligament narrow, almost covered. 

 Hinge very narrow, teeth almost obsolete, lateral narrow; 

 muscular impressions superficial ; nacre bluish, livid towards 

 the umbones. 



Length 42, height 25, diam. 12 mm." (Strubell). 



Type locality, South Sumatra. 

 Microcondylcra bicristata Strubell, Nachr. D. Mai. Ges., 1897. 



p. 9. 



I am indebted to the courtesy of Dr. F. Haas for the correct 

 generic position of this species. 



Section Nasus Simpson, 1900. 



N'astLs Simpson, Syn., 1900, p. 839. 



Shell somewhat solid, rather inflated, much elongated, with 

 a well-developed posterior ridge, with a low, faint one above 

 it, bluntly pointed at post-basal part ; beaks not high, eroded in 

 the specimens seen ; epidermis dark ; teeth compressed, high. 



Animal unknown. 



Type, Pseudodon nankingensis Heude. 



PSEUDODON NANKINGENSIS (Heudc). 



Shell rather thin, long elliptical, inflated, inequilateral ; beaks 

 not elevated ; posterior ridge high, subangulate ; anterior end 

 rounded ; dorsal and ventral outlines lightly curved ; posterior 

 end bluntly pointed or rounded, somewhat drawn out; surface 



