IigO PSEUDAVICULA 



Arconaia conjuncens (Heude). 



Shell somewhat delicate, elongated not A^ery solid, but 

 slightly curved or twisted ; posterior ridge rather high and 

 pinched up on the outer valve, ending in a point on the median 

 line ; anterior end almost regularly rounded, slightly angled, 

 but wholely wanting a wing above ; surface smooth ; pseudo- 

 cardinals subcompressed, rather short ; laterals long and nearly 

 straight ; muscle scars impressed, the posterior ones long and 

 oblique. 



Length 80, height 21 mm. 



China. 

 Uriio contortns var. conjungcns Heude, Conch. Fluv. Nank., 



II, 1877, pi. XV, fig. 33. 

 Arconaia conjungcns Simpson, Syn., 1900, p. 860. 



Heude also makes this a variety of A. lanccolata, but states 

 that both his varieties are probably species. This is much more 

 delicate than lanccolata, is smaller, smoother, less solid, less 

 twisted and curved and has difiFerent pseudocardinals. His 

 description is very meagre. 



Genus PSEUDA^aCULA Simpson, 1900. 



Pseudavicnla Simpson, Syn., 1900, p. 860. 



Shell with a well-developed anterior and posterior dorsal 

 wing; dorsal line strongly incurved; beaks full, not high; a 

 high, down-curved posterior ridge runs to the posterior basal 

 point, and between this point and the posterior point of the 

 wing the outline is deeply incurved ; base and lower part of 

 anterior end rounded ; surface slightly sculptured with con- 

 centric ridges ; beak sculpture probably zigzag rayed ; anterior 

 tooth of left valve elongate, slightly corrugated, that of the 

 right double ; laterals in left valve double, single in the right, 

 straight, elongated, thin, and prominent ; nacre rose-tinted. 



Animal unknown. 



Type, Unto johnstoni Smith. 



PSEUDAVICULA JOHNSTONI (Smith). 



Shell irregularly rhomboid, compressed, rather thin, inequi- 

 lateral ; dorsal margin an inverted arch, the anterior and pos- 

 terior ends of which extend into wings ; beaks slightly elevated ; 



