THE NATURAL HISTORY SURVEY. 79 
lacks the angulate character of the posterior slope; the cardinal 
teeth also present some differences, being more massive and ¢ 
diverging in coccinea than in the present species. The plate of 
the lateral teeth is also broader in coccinea. Specimens ex- 
amined June 2, 1897, had both gills filled with embryos. 
17. Quadrula coccinea Lea, pl. xiv., fig. 1; pl. xix., fig. 3. 
Unio coccineus Lea, Trans. Amer. Phil. Soc., Vol. VI., p. 12, pl. v., fig. 
12, 1884. 
Unio gouldii (gouldianus) Lea, Trans. Amer. Phil. Soc., Vol. X., p. 76, pl. 
vi., fig. 16, 1845. 
Shell: Roundly quadrate, or roundly elliptical, somewhat 
compressed, thick and solid; rounded before, squarely truncated 
behind, sometimes much produced; dorsal and ventral borders 
curved; surface roughened by growth lines which are more or 
less sharp and elevated; umbones elevated, rather compressed, 
reddish brown, marked by three large, elevated, undulating 
wrinkles and numerous fine growth lines; anterior umbonal 
slope rounded, posterior slope flat, subangulated, and some- 
times excavated; ligament short, wide, strong, very dark brown 
or horn; epidermis brownish or reddish brown, shining; cardinal 
teeth double in both valves, nearly equal in the left, the anterior 
tooth but a rudiment in the right valve, all depressed, triangu- 
lar, thick, heavy, strongly serrated, the anterior tooth in the left 
valve being long and narrow; lateral teeth rather long, elevated, 
lamellar, serrated, directed ventrally; the single lateral in the 
right valve has a depression into which the ventral tooth in the 
left valve fits; connecting plate between the teeth wide and 
spreading, thin, flat, smooth; anterior adductor muscle scar a 
Jittle longer than wide, deeply excavated, rounded below, trun- 
cated above, striated; posterior adductor muscle scar roundly 
quadrate, slightly impressed, striate, confluent; protractor pedis 
muscle scar wider than long, very deeply excavated, striated; 
dorsal muscle scars situated on the posterior face of the poste- 
rior cardinal tooth in the left valve very deep, long and narrow; 
cavity of the beaks shallow; pallial line barely visible; nacre 
rose, pink or salmon pink, iridescent; in some specimens the 
nacre is white. 
Length, 52.50; height, 39.50; breadth, 20.00 mill. (10088). 
a 1.0 
61.00; ‘ 56.00; ot 33.00 ‘* (12992). Hybrid. 
a THOO;) > 82. °60,00: te 28.00 '' (12944), 
a 66.00; ‘ 54.00; 32.00. ** (12944), 
Animal; Generally a delicate flesh color, shading to bluish 
