BILLINGSELLID^. 747 



The most strikmg feature is the presence of two strong radiating ridges tliat originate near 

 the beak and extend forward nearly to the frontal margin. These ridges may be tlie casts of 

 the main vascular sinuses or it may be tliat they represent 

 ridges on the exterior of the shell, one on each side of the 

 shallow median sinus. At present, with the material before 

 me, I am inclined to the view that they represent the casts 

 of sinuses and hence the provisional generic reference to 

 Wimanella. 



Nothing is Itnown with certainty of the outer surface 

 or of the substance of the shell. The interior casts and the 

 matrices of the casts show two strong radiating ridges, the a B 



shell substance havmg apparently been removed and its ytcvuE m.-wimanciia tnynemis wnicott. a, b, 



1 1 i_ 1 j_i ■ i> J 1 T i 1 i* 'i Narrow and broad forms showing the two Strong 



place lost by the compression Ot the sediment before its ridgesonthecastthataresupposed to represent 



consolidation. ^^^^ main vascular sinuses (U. S. Nat. Mus. Cat. 



mi ./^ • 1 ■ 1 c T /~i J i-1 T Nos. 52255a and 52255b, respectively). 



ihe specmc name is derived from inyo County, Call- _ * , , t ,•* =>. 



^ J j7 Ihe specunens represented are from Locality 8b, 



lOrnia. Lower Cambrian, Inyo County, California. Figure 



e.3A is copied from Walcott [190Sd, PI. X, fig. 4). 

 Formation and locality. — Lower Cambrian: (8b) Limestones in it represents the type specimen. 

 Tollgate Canyon, about 15 miles (24.2 km.) east of White Pine, White 

 Mountain Range, Inyo County, California. 



Wimanella saffoedi (Walcott). 

 Plate LXXXVII, figures 7, 7a. 



BilUngsella saffordi Walcott; 190-5, Proc. U. S. Nat. Mus., vol. 28, p. 244. (Described and discussed as below as a 

 new species."! 



General outUne of ventral valve subsemicircular and of dorsal valve transvei'sely broad 

 oval; greatest width of A^alves at about the center; hinge Hne straight and a little shorter than 

 the greatest width of the shell. A typical ventral valve has a length of 9 mm., width 9 mm. 

 Dorsal valve, length 10 mm., width 12 mm. Biconvex, the ventral valve being more elevated 

 at the umbo than the dorsal. Surface, so far as known, smooth or marked by concentric 

 strife, and lines of growth. 



Ventral valve with umbo curvmg over and terminating in the small apex that incurves a 

 little over the area; area about one-half the elevation of the valve; a broad delthyrium is partly 

 covered by a convex deltidium; casts of the interior indicate a low, tripartite pseudospondylium 

 and one cast shows strong main vascular sinuses extending from the lateral divisions of the 

 pseudospondylium nearly to the front margin. Dorsal valve with low area and small pseudo- 

 cruraUum; the casts are too imperfect to show any other details. 



Observations. — This species occurs in the same region as Wimanella harlanensis (Walcott) and 

 also has a smooth shell; it differs in being of equal length and breadth and in having less strongly 

 marked interior characters. 



The specific name is given in recognition of the work of Mr. J. M. Safford upon the geology 

 of Tennessee. 



Formation and locality. — Middle Cambrian: (14a) Sandstone of the Rome formation, along First Creek Gap, 

 4 miles (6.4 km.) north-northeast of Knoxville [Keith, 1905, areal geology sheet], Knox County, Tennessee. 



Wimanella shelbyensis Walcott. 

 Plate II, figures 9, 9a. 



Wimanella shelbyensis Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, p. 100, PL X, fig. 3. (Described and 

 discussed as below as a new species. Fig. 3 is copied in this monograph, PL II, fig. 9.) 



All the specimens representmg this species in the collection are flattened in the shale to 

 such an extent that very little of the original convexity of the shell is retained, and only the 

 impression of the shell remains, as the shell substance has been entirely removed, probably by 

 solution. The general form of tliis species resembles very closely that of BilUngsella PappalacTiia. 



