gt4 QUADRULA 
Unio plumbeus Kuster, Conch. Cab. Unio., 1862, p. 289, pl. 
KEVIL Ss) Le 2: 
Chemnitz’ figures are not carefully finished and they, no 
doubt, give an erroneous representation of the pseudocardinals. 
The outline is nearly orbicular ; the shell is evidently very solid. 
QuAPRULA COREANA (von Martens). 
Shell subelliptical, inequilateral, not inflated, rather solid; 
beaks moderately full and elevated, their sculpture not ob- 
served; posterior ridge moderately developed, rounded; sur- 
face strongly sculptured, there being a row of heavy chevron- 
shaped folds down the posterior ridge, while the anterior end 
_ 1s somewhat pustulous ; epidermis yellowish-green, with green- 
ish cloudings; left valve with two radial pseudocardinals, the 
hinder heavier, and two remote, delicate laterals; right valve 
with one pseudocardinal and two vestigial ones, with one 
vertically striate, slender lateral; anterior scars small, poste- 
rior scars faint; beak cavities very deep, compressed; nacre 
white, thinner behind. 
Length 43, height 36, diam. 21 mm. 
Seoul, Korea. 
Unio coreanus von Marvrens, S. B. Nat. Fr., 1886, p. 78; 
Zool. Jahrb. Suppl., VIII, 1904, p. 50, pl. m1, fig. 5. 
Ouadrula coreana SIMPSON, Syn., 1900, p. 797. 
“Among the Chinese species figured by Heude, Unio affinis, 
(Ouadrula similaris Simpson), is the nearest to this Korean 
species, but in the Chinese species the anterior end is much 
shorter, so that the form is in a general way more triangular, 
the folds of the posterior portion are stronger and less nu- 
merous, the tubercles are arranged in concentric rows and are 
longer in this direction; towards the beaks the rows are 
oblique.” (von Martens). 
A single specimen belonging to the collection of Mr. Fred- 
erick Stearns, from Seoul, Corea, which seems to be von 
Martens’ species, is here described. ‘The specimen was taken 
dead and the surface is slightly worn. It is apparently a more 
compressed, less solid species than the Chama plumbea of 
Chemnitz, to which it seems to be closely related. 
