lO SMITHSONIAN MISCPILLANEOUS COLLECTIONS VOL. 97 



This species is characterized by the erectness of the ventral valve 

 so that the false area is about at right angles to the base of the shell. 



Upper Cambrian; (loc. 8 o) 2 miles north of Aiirum, Schell Creek- 

 Range, Nevada. 



Cotypes. — U.S.N.M. no. 52119. 



BILLINGSELLir3AE Schuchert 



WIMANELLA Walcott, 1908 



Wimanella walcotti, n. sp. 



WimancUa simplex Walcott (part), U. S. Geo!. Surv. Mon. 51, p. loi, text 

 fig. 64, 1912; Smithsonian Misc. Coll., vol. 67, no. 2, p. 26, pi. 4, figs. 7-7C, 

 1917. 



This species is represented Ijy many specimens in fine-grained, 

 hard shale. Most of the ribbing and growth lines have been smoothed 

 out by pressure. Fine ribs show in cross light and the growth lines 

 must have been rather stronger than usual. The hinge line is straight 

 and the undistorted valve forms a little more than a semicircle. 



Middle Cambrian, Ross Lake; (loc. 63J) Popes Peak, i| miles 

 south of Stephen ; and i mile east of Hector, Mount Bos worth, 

 British Columbia. 



Cotypes. — U.S.N.M. nos. 63713-5, 51407. 



Wimanella rossensis, n. sp. 



IVimanclla simplex Walcott (part), Smithsonian Misc. Coll., vol. 67, no. 2, 

 p. 26, pi. 4, figs. 8-8c, 1917. 



Limestone nodules in the Ross Lake shale contain an abundant 

 fauna among which is a species of Wiuianclla different from [['. tiKil- 

 catti in the enclosing shale. Preservation in granular limestone in 

 contrast to partial flattening in shale, accounts for some of the differ- 

 ences at first apparent. However, not all can thus be accounted for. 

 W. rossensis is much higher in the ventral valve, thus creating a 

 larger area. Growth lines are heavy, but vary more in size than in 

 JV. walcotti. 



Middle Cambrian, Ross Lake; (loc. 63 j) Popes Peak, i^ miles 

 south of Stephen; and i mile east of Hector, Mount Bosworth, 

 British Columbia. 



Cotypes. — U.S.N.M. nos. 64716-9. 



