QUADRULA 927 
Group of Quadrula triclava. 
Shell solid, elongate triangular, obtusely pointed at the pos- 
terior base, with a decided posterior ridge, along which runs 
a row of ponderous knobs; beaks high and far forward; sur- 
face strongly nodulous; posterior slope slightly corrugated ; 
epidermis dark chestnut; pseudocardinals heavy, subradial, 
radially striate; laterals vertically striate, secondary lateral of 
right valve well developed; cavity of the beaks enormously 
deep and compressed; a granular callus behind the laterals; 
nacre silvery, radially, granularly striate outside the pallial 
line. 
Animal unknown. 
QUADRULA TRICLAVUS (Heude). 
Shell long, triangular, solid, scarcely inflated, very inequi- 
lateral ; beaks elevated, somewhat compressed ; posterior ridge 
high, ending near the base in a blunt point ; anterior end round- 
ed and somewhat cut away below; base line nearly straight; 
outline of the dorsal slope lightly curved; along the posterior 
ridge there is a row of ponderous knobs; the rest of the disk, 
except the anterior end, is covered with irregular nodules; 
epidermis brownish; pseudocardinals strong, radial, slightly 
curved, granularly striate; laterals vertically striate, that in 
the right valve somewhat double; beak cavities enormously 
deep ; compressed; posterior callosities well developed ; pallial 
line remote; nacre white, iridescent behind. 
Length 110, height 72, diam. 37 mm. 
China. 
Unio triclavus Heupr, Conch. Fluv. Nank., II, 1877, pl. x, 
fies. 27, DTG. 
Ouadrula triclava Stmpson, Syn., 1900, p. 800. 
A remarkable Naiad, its most prominent character being a 
row of four or five large, elevated knobs running down the 
posterior ridge. 
Group of Oucdrula bazint. 
Shell elongate-trigonal, with a fairly well developed poste- 
rior ridge, pointed behind: beaks not high, almost at extreme 
front of the shell: surface more or less covered with knobs 
