12 THE AMERICAN MIDLAND NATURALIST 
distinguished from this by a greater compression, lower beaks, no 
full median radial swelling and an absence of a radial depression 
in front of the posterior ridge. There are, however, intermediates 
that can not be satisfactorily named. The shell is roundly quadrate 
or roundly elliptical, rounded before and squarely truncated behind. 
The surface is roughened by sharp and elevated lines of growth; 
older specimens show considerable erosion. The umbones are 
elevated and bear three large, elevated undulating wrinkles and 
many fine lines of growth. There is a short, wide and strong liga- 
ment, of a dark brown or horn color. The epidermis is brown or 
reddish brown; in very old specimens it becomes chalky. The 
cardinal teeth are double in both valves, nearly equal in the leit, 
the anterior tooth only a rudiment in the right valve. The cardinal 
teeth are depressed, triangular, heavy and strongly serrated. 
The lateral teeth are long, elevated serrated and directed ventrally. 
The single lateral in the right valve has a depression into which 
the ventral tooth in the left valve fits. The anterior adductor 
muscle scar is deeply excavated and striated, and longer than wide; 
the posterior adductor muscle scar is slightly impressed, striate 
and confluent. The cavity of the beaks is shallow. The pallial 
_line is barely visible to quite deeply impressed. The nacre is variable 
from a cloudy white to rose, pink or salmon color. 
Length 47 Height 35 Diameter 22 
71 53 28 
78 5% 34 
96 64 38 
1ro8 79 50 
OQUADRULA _TUBERCULATA (Rafinesque). 
Obliquaria (Roiundaria) tuberculaia Rafinesque, Ann. Gen. Sci. Brux. V, 
1820, p. 103. ; z . 
Rotundaria tuberculata Agassiz, Arch. fuer Naturg., I, 1852, p. 48. 
Unto tuberculatus Conrad, Monog., V, 1836,.p. 43, pl. XXII. 
Quadrula tuberculaia Simpson, Syn., 1900, p. 795. 
Unio verrucosus Barnes, Am. Jl. Sci., VI, 1823, p. 123, pl. V., fig. 6. 
Margarita (Unio) verrucosus Lea, Syn., 1836, p. 16. 
Mya verrucosa Eaton, Zool. Text-Book, 1826, p. 216. 
Quadrula verrucosa Baker, Moll. Chi., Pt. I, 1898, p. 85, pl. XXIII. 
Unto tuberculosa Valenciennes, Rec. Obs. Zool. Anat., II, 1833, p. 232. 
The shell of this species is quadrate, thick, heavy and pustulate. 
The dorsal margin is nearly straight while the ventral margin is 
rounded to straight. The surface of the shell is very rough,—the 
roughness being caused by coarse lines of growth, tubercles and 
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