748 CAMBRIAN BRACHIOPODA. 



The casts show a strong cardinal area on the ventral valve, with a broad delthyrium, but not a 

 pseudodeltidium; the dorsal valve has a narrow cardinal area with a broad open delthyrium. 



The exterior surface is marked by fine concentric Imes and a few stronger varices of growth. 

 A small ventral valve has a length of 8 mm., with a width of 10 mm. A larger one has a length 

 of IS mnl.; width, 22 mm. A small dorsal valve has a length of 10 mm.; width, 13 mm.; and 

 the largest dorsal valve in the collection has a length of 19 nim.; width, 25 mm. 



None of the specimens show any traces of vascular or muscular markings; in this respect 

 resembhng Wimanella? anomala (Walcott) (PI. LXXXVII) and Billingsella? appalachia Walcott 

 (PI. LXXXVII). 



This species appears to be the Lower Cambrian representative of W. ? anomala of the Middle 

 Cambrian, differing from the latter in ha-^dng rounded cardinal angles instead of the acute 

 projecting angles so characteristic of W. f anomala. BiUingsella ? appalachia has the same general 

 form as W. shelhyensis, but the latter differs from it in having a smooth surface and m the absence 

 of all traces of radiating ribs. 



It more nearly resembles Wimanella simplex Walcott (PI. LXXXIX, fig. 2). It differs 

 from the latter in being more transverse, and the cast of the umbonal cavity is relatively smaller. 



It is a curious fact that in all the species of Wimanella mentioned there is no trace of a 

 vascular marldng or muscle scar. All the species occur in argillaceous shale, and none of them 

 preserve the shell substance. The shells appear to have been macerated and removed by 

 solution, leaving only a cast of the compressed inner or outer surface of the valve. 



The specific name is derived from Shelby County, Alabama. 



Formation and locality. — Lower Cambrian: (17b) Shale in Rome (" Montevallo") formation, 4 miles (6.4 im.) 

 south of Helena; and (56o) shale in Rome ("Montevallo") formation along road just north of Buck Creek, 1.125 miles 

 (1.8 km.) northeast of Helena; both in Shelby County, Alabama. 



Wimanella simplex Walcott. 

 Text figure 64; Plate LXXXl'X, figures 2, 2a-e. 



Wimanella simplex Walcott, 1908f, Smithsonian Misc. Coll., vol. 53, No. 3, p. 101, PI. X, fig. 2. (Discussed as below 

 as a new species. Fig. 2 is copied in this monograph, PI. LXXXIX, fig. 2.) 



The general form of this species is much like that of BiUingsella coloradoensis, except that 



the beak of the ventral valve rises above the hinge line, much as ini?. highlandensis (PL LXXXVII, 



figs. 4, 4a). The surface of W. simplex appears to be smooth except for 



r'~"l§^^^s» 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 (fig. 2e) indicates that the 



1^^' T beak of the dorsal valve was slightly elevated above the liinge line; it 



^||^ ^,- is probable that figure 2 represents a dorsal valve. All the specimens 



are flattened in shale, and the shell substance has been removed by solu- 



FiBiTRE 6i.— Wimanella simplex . . , • • r- , i j ■, , ■ c 



Walcott. Interior of a com- tioii. llie material IS uusatislactory, but as it represents a species oi 

 pressed dorsal valve. Found ^^^g smooth type from a knowii horizon in the Middle Cambrian, it is 



in Locality 35c, in a drift . i • •£• 



block of Lower Cambrian illustrated and given a specific name. 



sliale on Mount Bosworth, „ , . ,. x ,, „ ^ . /„j \ 7 j, 



British Columbia (U.S. Nat. FORMATION AND LOCALITY. — Lower Cambrian: (4v) About 200 feet (61 m.) above the 



Mus. Cat. No. .51407). iinconform,able base of the Cambrian and 75 feet (22.9 m.) above the top of the quartzitic sand- 



stones in a shale which corresponds in stratigraphic position to shale No. 6 of the Dearborn 

 River section [Walcott, 190Sf, p. 202], Gordon Creeh, 6 miles (9.6 km.) from South Fork of Flathead River; and (4ci and 

 4w) about 315 feet (96 m.) above the unconformable base of the Cambrian and 190 feet (57.9 m.) above the top of the 

 quartzitic sandstones in a shale which corresponds in stratigraphic position to shale No. 6 of the Dearborn River 

 section [Walcott, 1908f, p. 202], on Youngs Creek, about 5 miles (8 km.) from its junction with Danaher Creek; both 

 in the Ovando quadrangle (U. S. Geol. Survey), Powell County, Montana. 



(35c) Drift blocks of siliceous shale supposed to have come from the Mount Whyte formation [Walcott, 1908f, 

 p. 214], 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. 



