NODULARIA 969 
NopuLARIA JAPANENSIS (Lea). 
Shell rhomboid elliptical, more or less elongated, convex, 
inequilateral, rounded in front, base line nearly straight, or 
somewhat curved, usually full behind the middle; posterior 
ridge but moderately developed, usually feebly double, ending 
in a faint biangulation below the median line; beaks not full 
or high, their sculpture zigzag-radial; surface more or less 
covered with nodulous sculpture, which is usually arranged in 
zigzags or chevron-shaped figures, the nodules often united 
together into corrugated ridges; epidermis varying from rich 
green in young shells to brown or black, dull or shining ; pseu- 
docardinals subcompressed to subsolid, rough, two in each 
valve, the upper one of the right valve small; laterals with 
traces of vertical striation; muscle scars not deep; beak cavi- 
ties shallow ; nacre dirty or lurid brownish. 
Length 62, height 33, diam. 19 mm. 
Length 40, height 30, diam. 15 mm. 
Japan. 
Unio japanensis Lua, Pr. Ac. N. Sci. Phila., III, 1859, p. 153; 
Wee Ne Sci, Phuila.- lV, 18600, p. 244; pl. xxxvi, fir. 123; 
Obs.,. VII, 1860, p. 62, pl. Xx xvi, fig. 123.—Kustrer, Conch. 
Cab. Unio, 1862, p. 227, pl. xcru, fig. 4.—Sowersy, Conch. 
Icon., XVI, 1868, pl. Lxxx, fig. 420. 
Margaron (Unio) japanensis Lea, Syn., 1870, p. 31. 
Nodularia japanensis Simpson, Syn., 1900, p. 809.—Haas, 
Con. Cab., Unio, 1910, p. 85, pl. viii, figs. 5-8. 
The type of this is not in the Lea collection, there being 
only a large shell, whose measurements are given above. The 
species varies considerably in the degree of sculpture, some 
specimens being only faintly nodulous, while others are strong- 
ly and densely sculptured throughout. 
Var. jokohamensis (von Thering). 
Differs from the typical form in being more blunt and 
rounded behind. It seems to be connected by intermediate 
forms. 
Japan. 
