4 REPORT ON-I'HE UNIONDAE OF ST. JOSEPH RIVER 7 
dorsal margin. ‘The ligament is snrall, short, thin and hardly pro- 
trudes above the valves. ‘The cardinal teeth are scarcely evident 
at all. The lateral teeth are single in both valves, long and straight. 
The pallial line is weakly impressed. The cavity of the shell is 
shallow; of the beaks, scarcely noticeable. The nacre is bluish 
to white; some specimens are spotted with yellowish brown. 
Length 85 Height 45 Diameter 27 
68 35 22 
78 42 24 
57 28 18 
PLAGIOLA DoNactFoRMIS (Lea). 
Unio donactformis Lea, Tr. Am. Phil. Soc., III, 1828, p. 267, pl. IV, fig. 3. 
Unto zigzag Lea, Tr. Am. Phil. Soc., III, 1829, p. 440, pl. XII, fig. 19. 
Unio nervosa Conrad, New F. W. Shells, 1834, p. 70. 
Unio nervosus Say, Am. Conch., VI, 1834. = 
Plagiola donaciformis Baker, Moll. Chi., Pt. I, 1898, p. 92. XIII, 4. 
Only one specimen of this species is at my disposal. The specimen 
measures 54mm. in length, 33mm. in height, and 12mm. in diameter. 
The specific name was evidently given to this shell on account of 
its resemblance to the marine genus Donax. ‘The species does not 
Seem to be common in this locality as but one specimen was found. 
It is a small, thick shell that can be recognized by its zigzag epider- 
mis, which, in the specimen before me is greenish and rayed with 
dark green. All the rays arise from the umbones and cover the 
entire disk. The shell is elliptically elongated, thick, solid and 
inflated. The lines of growth are indicated by obtuse ridges. The 
umbones are slightly elevated, much inflated, light brown in color, 
and marked by very fine ridges. There is a short ligament, rather 
wide and of a dark horn color. ‘The cardinal teeth are double in 
the left and single in the right valve, small, elevated, narrow, some- 
what triangular and coarsely serrated. The single tooth in the 
right valve is acutely triangular. The lateral teeth are long and 
directed ventrally. The anterior adductor muscle scar is longer 
than wide and deeply excavated. ‘The posterior adductor muscle 
scar is barely visible. ‘The pallial line is slightly impressed. ‘The 
cavity of the beaks is rather deep. The nacre is silvery white and 
iridescent. 
ANODONTA GRANDIS (Say). 
Anodonta grandis Say, New Harm. Diss., Vol. II, 22, p. 341, 1829. 
Anodonta plana Lea, Tr. Am. Phil. Soc. 2nd. ser. Vol. V., p. 48, 1834. 
Anodonta declivis Conrad, Am. Jl. Sci. & Arts, 1st. ser. Vol. XXV.p. 341,1836. 
