DESCRIPTION OF GENERA AND SPECIES. 22] 
This species differs from Aluta flexilis Matthew [1896, p. 198] in having a 
straight hinge-line; in this respect it resembles some forms of Leperditia. For 
the present it is referred to Aluta on account of its close resemblance to Aluta 
sterope. 
The specimens were collected from a fragment of compact, bluish-gray, thin- 
bedded limestone containing fragments of a trilobite that suggests Dorypyge. 
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, 1907c¢, 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 sterope (Walcott). 
Plate 23, Figure 14. 
Bradoria sterope WALcorr, 1905, Proc. U. S. Nat. Mus., vol. xxrx, p.101. (Species described as below.) 
Outline of shell obliquely semicircular. Hinge-line straight, nearly as long as 
the width of the valve; anterior cardinal angle about 80°; anterior curve obsolete; 
from the anterior cardinal angle the margin slopes downward and slightly inward, 
curving gently into the broadly rounded lower margin; posterior cardinal angle 
slightly obtuse; posterior margin curves gently from the angle to the broad curve 
of the lower side of the valve, which gives a broadly rounded posterior end. ‘The 
valve is rather strongly convex, rising to the greatest height near the center. The 
surface is marked by a very narrow rim; from the anterior cardinal angle a narrow 
ridge extends obliquely inward about one-half the distance toward the center, and 
terminates in a slight tubercle; on the anterior side there are three shallow depres- 
sions, as though the surface had been indented; on the posterior side there is one 
larger depression directly back of the tubercle at the end of the ridge, and a slight 
depression in the angle formed by the palpebral ridge, the hinge-line and the ridge 
between the two depressions. 
Surface with minute scattered puncte, as seen under a strong lens. 
The valve has a width of 1.125 mm.; length, 0.8 mm.; depth, about 0.25 mm. 
In outline this species resembles Aluta fragilis [p. 226]; it differs in its stronger 
shell and distinctly marked ridge and 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. 
i 
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} 
Aluta woodi (Walcott). 
Plate 23, Figure 15. 
Bradoria woodi WALCOTT, 1905, Proc. U.S. Nat. Mus., vol. xxrx, p. 102. (Species described as below.) 
Outline of shell obliquely semicircular. Hinge-line straight, a little shorter 
than the’greatest width of the shell; anterior cardinal angle about 70°; posterior 
cardinal angle obtuse; the posterior margin has a gentle curvature from the angle, 
which gives it a broadly rounded outline down to where it merges into the broadly 
rounded lower side; anterior margin almost straight and then gently curving into 
the lower margin. Surface rather convex, with the highest portion at the ridge 
around the central depression; the outer rim is very narrow and slightly rounded; 
from the anterior cardinal angle a narrow, sharp ridge extends obliquely inward 
