NODULARIA 957 
straight, in the left valve two, slightly rugosely sulcate, in the 
right valve one, slightly transversely sulcate. Anterior muscu- 
lar inipression large, round, very near to the anterior margin; 
pallial line in front rather wide, pitted, simple behind. 
Length 125, height 34, diam., under the beaks 15 mm. Beaks 
situated at 1-6 of the length, ligament extends to 4-6 of the 
length.” (von Martens). 
Type locality, Naemigang River, near Hatanggyong, and in 
a tributary of the Imjingang, Korea; also in the Kwanchon- 
gang near Pukchan, north of Naga-Naju. 
Unio acrorhynchus VON Martens, 5. B. Nat. Fr., 1894, p. 214. 
—Simpson, Syn., 1900, p. 861. 
Unio (Lanceolaria) acrorhynchus von Martens, Zool. Jahrb., 
Supple Vi 2905. p:.53, pl. 1, fis. 4. 
Lanceolaria acrorhyncha Haas, Con. Cab., Unio, 1910, p. 61, 
pl. v, fig. 4. 
“Groups with the Chinese U. grayanus Lea and the Japan- 
ese U. oxyrhynchus Marts., but larger and proportionately 
more compressed than either, not so low as grayanus and in 
the general appearance more like oxyrhynchus, but longer and 
at the posterior end more equally pointed above and below, 
whereas in oxyrhynchus the posterior part of the basal margin 
scarcely ascends, so that the point is lower; also in acrorhyn- 
chus the carina from the beaks to the posterior end is more 
prominent. With reference to the sculpture, in grayanus the 
vertical folds are more regular, more numerous, about 20, and 
consequently closer and also smaller, in LU. acrorhynchus they 
are less numerous, about 8, broader and irregular, in U. oxy- 
rhynchus they are similar, but decidedly weaker. On com- 
parison of adult examples, the differences are very clear, but 
the young shells resemble each other very much and especially 
in a young example of U. acrorhynchus from Massangabe, 
which has the same diameter as U. grayanus of the same size.” 
NopuLARTA OXYRHYNCHA: (von Martens). 
Shell elongated, subsolid, scarcely inflated, inequilateral ; 
posterior ridge full, pinched up, cord-like, ending behind in a 
point at or above the median line ; anterior end rounded, some- 
