924 QUADRULA 
Unio polystictus Hgupr, Conch. Fluv. Nank., II, 1877, pl. xu, 
hig. 25. 
Quadrula polystictus SIMPSON, Syn., 1900, p. 799. 
Unio polysticto-scriptus Heupr, Conch. Fluv. Nank., II, 1877, 
pl. x11, fig. 26. 
Quadrula polysticto-scriptus SIMPSON, Syn., 1900, p. 799. 
Unio scripto-polystictus Heupre, Conch. Fluv. Nank., II, 1877, 
pl. Xui; fig. 26: 
Unio scripto-polystrictus PayreL, Conch. Sam., III, 1890, p. 
107. 
Heude remarks that some of the species of this group ap- 
parently hybridise and it is quite likely he is correct. The 
same remark might be applied to some of the Anodontas of 
the woodiana group, on which he has so lavishly bestowed 
specific names. I have before me a shell of Unio polysticto- 
scriptus from the author, which does not exactly agree with 
that form or U. scripto-polystictus. ‘The National Museum 
specimen is something like Q. nodulosa, but is more decidedly 
rhomboid and more strongly nodulous. Heude’s figures of 
his two species slightly recall the Q. leat of Gray. After 
further study of these forms I think it best to place them under 
polystrictus as synonyms, as it does not seem to me that any 
clear specific lines can be established. The species as above 
constituted is scarcely, if at all, twisted on its axis. 
QUADRULA SIMILARIS Simpson. 
Shell subrhomboid, solid, inflated; beaks rather full and 
high, subterminal; anterior end rounded, somewhat slopingly 
cut away below; base rounded; outline of dorsal slope curved, 
raised almost to an angle behind the ligament ; umbonal region 
covered with narrow, oblique, corrugated ribs, which run 
nearly parallel with the dorsal line; surface generally, except 
the extreme anterior end, covered with pustules; dorsal slope 
with strong, curved ridges; epidermis brown; pseudocardinals 
strong, radial, split up into regular divisions; lateral in the 
right valve somewhat double; beak cavities deep, compressed ; 
nacre white, thinner behind. 
Length 85, height 70, diam. 42 mm. 
China. 
