THE NATURAL HISTORY SURVEY. 89 
and a single lateralsometimes with a supplementary one below; 
cavity of the beaks rather shallow; anterior part of the shell 
very solid, posterior part much thinner. 
Animal: Anal opening with only slight crenulations, branchial 
opening having numerous papille; mantle very thin with a 
broad, thick margin; branchiz small, round below, inner much 
the larger, free nearly its whole length from the abdominal sac; 
marsupium consisting of from six to ten distinct ovisacs about 
the center of the outer gill or just behind it, which, when gravid, 
project far below the rest of it. (Simpson.) 
23. Obliquaria reflexa Rafinesque, pl. xiv., fig. 5; pl. xx., fig. 2. 
Unio reflexus RAFINESQUE, Mon. des Coq. Biv. it Fluv. Ohio, p. 306, 1820. 
Unio cornutus BARNES, Amer. Jour. Sci. and Arts, lst series, Vol. VI., p. 
122, figs. 5a, db, 1823. 
Shell: Roundly ovate, thick, heavy, inflated, broadly rounded 
before, triangular behind; dorsal border rounded, ventral border 
with a profound bulge; surface smooth, the lines of growth 
being very fine, ornamented by four large nodules which are 
placed in the center of the surface on a line drawn from the 
umbones to the central bulge; on the umbones the nodules are 
rounded, but as they near the ventral border they become very 
long and narrow; umbones elevated, inflated, ornamented with 
four large nodules and numerous fine, concentric growth lines, 
color light brown; anterior umbonal slope very broad and 
rounded; posterior slope excavated, with a strong shoulder 
extending from the umbones to the ventral border, making the 
shell strongly angular; ligament short, very wide, strong, dark 
brown; epidermis light grass green, yellowish greenor brownish; 
some specimens are marked by numerous wide green or black 
rays, which are made up of more or less interrupted lines or 
zigzag shaped marks; cardinal teeth double in both valves, 
équalin the left valve and the posterior tooth much the smaller 
in the right valve, massive, heavy, broadly triangular, diverging, 
very heavily grooved; lateral teeth short, thick, serrated, 
directed ventrally; connecting bridge very thick, broad, flat, 
smooth; anterior adductor muscle scar longer than wide, very 
deeply excavated, strongly striated; posterior adductor muscle 
scar rounded, impressed, striated, confluent, iridescent; jpro- 
tractor pedis muscle scar wider than long, deeply excavated, 
striated; dorsal muscle scars numerous, situated on the poste- 
rior face of the cardinal teeth, small, deeply pitted; pallial line 
