226 RESEARCH IN CHINA. 



latter is in about the same position as the tubercle on A. bergeroni [p. 225] but A. 

 bergeroni is quite different in its outline and convexity. 



Formation and Locality. Middle Cambrian : (C 32) A fine-grained bluish-black 

 limestone bowlder believed to have come from the lower part of the Ki-sin-ling 

 limestone [Blackwelder, igojc, p. 272] ; collected in river drift i mile (1.6 km.) south 

 of Chon-p'ing-hien, on the Nan-kiang River, southern Shen-si, China. 



Collected by Bailey Willis and Eliot Blackwelder. 



Aluta eris (Walcott). 



Plate 23, Figure 12. 

 Bradoria eris WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 100. (Species described as below.) 



General outline obliquely semicircular. Hinge-line straight; anterior cardinal 

 angle about 70; posterior cardinal angle slightly obtuse; anterior margin nearly 

 straight to where it merges into the rounded lower margin ; posterior margin gently 

 rounded from the angle down to where it merges into the lower margin. Surface 

 moderately convex, with the highest point at the tubercle a little in front of the 

 center; a very narrow rim extends from the posterior cardinal angle around to the 

 anterior side, where it broadens out and continues to the anterior cardinal angle; 

 a slight, narrow ridge extends obliquely inward a short distance from the anterior 

 cardinal angle to a furrow that extends from the hinge-line at right angles a short 

 distance; the ridge and furrow outline a small lobe; from the inner angle, formed 

 by the furrow and ridge described, a very narrow ridge extends downward, sub- 

 parallel to the anterior margin, to the base of a strong, elevated tubercle or spine 

 that is situated on the anterior third a little in advance of the transverse center of 

 the valve. 



Under a strong lens the surface appears to be slightly roughened by shallow 

 punctae. 



Width, 2 mm.; length, 1.5 mm.; depth, about 0.5 mm. 



This species differs from Aluta sterope [p. 227] in the outline of its valve and the 

 presence of an elevated tubercle near the center. 



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(7, p. 272] ; collected in river drift i mile (1.6 km.) south 

 of Chon-p'ing-hien, on the Nan-kiang River, southern Shen-si, China. 



Collected by Bailey Willis and Eliot Blackwelder. 



Aluta fragilis (Walcott). 

 Plate 23, Figure 13. 



Bradoria fragilis WALCOTT, 1905, Proc. U. S. Nat. Mus., vol. xxix, p. 100. (Species described as 

 below.) 



Hinge-line nearly straight, about one-fifth shorter than the width of the valve ; 

 posterior cardinal angle obtuse, with the marginal curve long and passing into the 

 broad curve of the lower end of the valve ; anterior cardinal angle about 75, with 

 the anterior margin nearly straight to where it merges into the broad curve of the 

 lower part of the valve. Surface of the valve wrinkled to such an extent that it 

 looks like wrinkled parchment. What may be an ocular tubercle occurs a short 

 distance from the hinge and anterior margin. 



Surface minutely punctate under a strong lens. 



Width, 2.25 mm. ; length, 2 mm. ; depth, unknown, as the flexible test has been 

 compressed. 



