CAMBRIAN BRACK lOPODA — WAI.COTT lOI 



WIMANELLA SIMPLEX, new species 



Plate io, Figure 2 



The general form of this species is much Hke that of BillingscUa 

 coloradoensis (Shumard) [i860, p. 627], except that the beak of the 

 ventral valve rises above the hinge line much as in B. highlandcnsis 

 (Walcott) [1886, p. 119]. The surface of W. simplex appears to 

 be smooth, except for a few concentric lines of growth. Nothing is 

 known of the interior except what is shown by the cast of the 

 umbonal cavity. A crushed specimen with the two valves flattened 

 out indicates that the beak of the dorsal valve was slightly elevated 

 above the hinge line. All of the specimens are flattened in shale, 

 and the shell substance has been removed by solution. The material 

 is unsatisfactory, but, as it represents a species of the smooth type 

 from a known horizon in the Middle Cambrian, it is illustrated and 

 given a specific name. 



Formation and Locality. — Lower Cambrian: (i) Shales on 

 Gordon Creek north of Gordon Mountain, 6 miles (p.6j km.) above 

 the South Fork of the Flathead River; and (2) Wolsey shales, 

 below Gordon Mountain, on Youngs Creek, about 5 miles (8.05 

 km.) from its junction with Danaher Creek; both in the Lewis and 

 Clark Forest Reserve, Montana. (3) Drift block supposed to have 

 come from the Mount Whyte formation, found on the south slope 

 of Mount Bosworth, a short distance northwest of the Canadian 

 Pacific Railway track, between Stephen and Hector, eastern British 

 Columbia, Canada. 



Genus BILLINGSELLA Hall and Clarke [1892&, p. 230] 

 BILLINGSELLA MAJOR, new species 



Plate 10, Figures i and I(7 



In general form and convexity this shell is related to BiUingsella 

 coloradoensis (Shumard) [i860, p. 627]. It differs from it in 

 being larger and in having coarser radiating ribs. It is the Upper 

 Cambrian representative of the latter species. 



Formation and Locality. — -Upper Cambrian : Fine-grained, 

 buff-colored sandstone in excavation on Wells' farm, 2 miles (3.22 

 km.) west of Baraboo, Sauk County, Wisconsin. 



