DESCRIPTION OF GENERA AND SPECIES. 225 
OSTRACODA. 
Genus ALUTA Matthew. 
Aluta bergeroni (Walcott). 
Plate 23, Figure ro. 
Bradoria bergeroni WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxrx, p. 99. (Species described as 
below.) 
General outline broadly semielliptical. Hinge-line straight, nearly as wide as 
the breadth of the valve; anterior cardinal angle about 80°; posterior cardinal angle 
slightly obtuse; the anterior margin is very slightly curved from the angle to where 
it merges into the broadly rounded front; posterior margin somewhat broadly 
rounded from the angle to the front. Surface convex, the greatest convexity being 
back of the transverse center between the ocular tubercle and the posterior fourth 
of the valve. From this elevated portion the surface slopes rapidly and somewhat 
abruptly to the hinge-line and more gently to the lower margin. From the anterior 
cardinal angle a very short, narrow ridge extends to a small, circular, slightly 
elevated tubercle which is situated about an equal distance from the hinge-line and 
the anterior margin. ‘The anterior, posterior, and lower margins have a narrow, 
rounded rim that is slightly flattened on the inner side. 
Surface marked by shallow, scattered puncte and very fine puncte, as seen 
under a strong lens. 
Width of valve, 1.8 mm.; length, 1 mm.; depth, about 0.5 mm. 
This species is distinguished from Aluta sterope |p. 227] by its greater width and 
the form of the ocular tubercle. 
Formation and Locality —Middle Cambrian: (C32) A fine-grained bluish-black 
limestone bowlder believed to have come from the lower part of the Ki-sin-ling 
limestone [Blackwelder, 1907¢, p. 272]; collected in river drift 1 mile (1.6 km.) south 
of Chén-p’ing-hién, on the Nan-kiang River, southern Shen-si, China. 
Collected by Bailey Willis and Eliot Blackwelder. 
Aluta enyo (Walcott). 
Plate 23, Figure 11. 
Bradoria enyo WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxrx, p. 99. (Species described as below.) 
General outline irregularly oval. Hinge-line about four-fifths the width of 
the valve; anterior cardinal angle nearly a right angle; posterior cardinal angle 
slightly obtuse; the anterior margin extends from the angle almost directly down- 
ward to where it curves and merges into the broadly rounded lower margin; pos- 
terior margin very slightly rounded from the angle downward to where it curves 
and merges into the lower margin. Surface moderately and uniformly convex, the 
highest portion being near the center; a very short, narrow, low, and somewhat 
obscure ridge extends obliquely inward from the anterior cardinal angle to a small, 
slightly elevated ocular tubercle; a slight furrow appears to extend from the tubercle 
obliquely to a point about midway of the hinge-line; a little posterior to this, and 
near the hinge-line, there appears to be a minute, low tubercle. 
The surface appears to be minutely punctate under a strong lens. 
Width of valve, 1 mm.; length, 0.75 mm.; depth, about 0.25 mm. 
This species is distinguished from A. sterope [p. 227] by the difference in the 
form of the anterior cardinal angle and the position of the ocular tubercle. The 
