PLATE XLVI. 
a. Central lateral space of area. f. Flexure line of area. 
a’. Outer lateral space of area. p. Pedicle groove. 
e. Trapezoidal area, including central, middle v. Visceral cavity. 
lateral, and outside lateral muscle scars. 
Oxso.ius (WESTONIA) AURORA (Hall) (p. 451). 
Ficure 1. Compressed ventral valve, from which the outer shell has been exfoliated. Locality S85x, Upper Cambrian 
sandstone near Mazomanie, Dane County, Wisconsin. U.S. Nat. Mus. Cat. No. 5168la. The area 
is enlarged in figure lc. 
la. Cast of the interior of a compressed ventral valve associated with the specimen represented by figure 1. 
The visceral area (v) recalls the heart-shaped pit of Lingulella acutangula (Pl. XVII, fig. 1f). The 
central muscle scars were located in the area (c), but are not clearly defined. U.S. Nat. Mus. Cat. 
No. 51681b. 
lb. Compressed ventral valve associated with the specimen represented by figure 1, showing concentric and 
radiating lines and strize as preserved on the cast of the interior of the shell. U.S. Nat. Mus. Cat. 
No. 5168le. The area is enlarged in figure 1d. 
1c. Enlargement of the area of figure 1. U.S. Nat. Mus. Cat. No. 51681a. 
1d. Enlargement of the area of figure 1b, to show the apron-like area mentioned in the text (p. 482;. U.S. 
Nat. Mus. Cat. No. 51681ce. 
le. Cast of the exterior of a dorsal valve associated with the specimen represented by figure 1. U. &. Nat. 
Mus. Cat. No. 51681d. 
1f. Cast of the interior of a dorsal valve associated with the specimen represented by figure 1. The shell is 
compressed and the area broken at x’. U.S. Nat. Mus. Cat. No. 51681e. 
lg. Enlargement of a portion of the central part of the surface of the shell figured in Jh, to show the irregular 
lamellose character of the striz. Locality 85s, Upper Cambrian sandstone at Prairie du Sac, Sauk 
County, Wisconsin. U.S. Nat. Mus. Cat. No. 51680a. ° 
lh. Part of the shell represented in figure lg, greatly enlarged by photography to illustrate the character of 
the outer surface. U.S. Nat. Mus. Cat. No. 51680a. 
152 
