PLATE XCIII. 
a. Cardinal area. j. Cardinal process. 
a’. Anterior adductor impressions. 
Tole 
= a 7 \y ascular markings. 
a’’. Posterior adductor impressions. nh 
b. Dental sockets. sp. Free spondylium or cast of it. 
d. Delthyrium. t. Teeth. 
d’. Cast of umbonal cavity. vs. Vascular sinus. 
FINKELNBURGIA OSCEOLA (Walcott) (p. 795). 
Fiaures | and 1b. Natural casts of ventral valves from Locality 78, Upper Cambrian sandstone in quarry near St. 
Croix River, in suburbs of Osceola, Polk County, Wisconsin. U.S. Nat. Mus. Cat. Nos. 52413a and 
52413b, respectively. 
la. Natural cast of ventral valve from Locality 79b, Upper Cambrian sandstone near Hudson, St. Croix 
County, Wisconsin. U.S. Nat. Mus. Cat. No. 52415a. 
1c and 1d, 1d’, and 1d’. Casts of the interior of a dorsal and a ventral valve from Locality 83!, Upper Cam- 
brian sandstone near Trempealeau, Trempealeau County, Wisconsin. U.S. Nat. Mus. Cat. Nos. 
52412a and 52412b, respectively. Figure 1d represents the type specimen. 
le. Natural mold of exterior of dorsal valve associated with the specimens represented by figures le and 1d. 
U.S. Nat. Mus. Cat. No. 52412c. 
-1f. Cast of interior of dorsal valve that shows casts of what may have been the points of attachment of the 
adductor muscles, associated with the specimens represented by figures lc and 1d. U.S. Nat. Mus. 
Cat. No. 52412d. 
1g. Cast of the interior of dorsal valve associated with the specimens represented by figures le and 1d. U.S. 
Nat. Mus. Cat. No. 52412e. 
lh. Imperfect cast of the interior of a dorsal valve from Locality 79a, Upper Cambrian sandstone at Menomo- 
nie, Dunn County, Wisconsin. U.S. Nat. Mus. Cat. No. 52414a. 
FINKELNBURGIA FINKELNBURGI (Walcott) (p. 794). 
Ficure 2. Cast of interior of ventral valve, the type specimen. What may be the cast of the base of the vascular 
trunks is shown (vs). U. S. Nat. Mus. Cat. No. 52410a. 
2a. Cast of interior of ventral valve, with outline of posterior view, showing area of adductor scars (a’). 
U.S. Nat. Mus. Cat. No. 52410b. 
2b. Cast of the interior of a ventral valve. U.S. Nat. Mus. Cat. No. 52410ce. 
2c. Cast of the interior of a dorsal valve. U.S. Nat. Mus. Cat. No. 52410d. 
2d. Cast of the interior of a ventral valve with the bases of very large vascular sinuses. U.S. Nat. Mus. Cat. 
No. 52410e. 
2e. Cast of interior of dorsal valve, with back and side outlines. U.S. Nat. Mus. Cat. No. 524108. 
The specimen represented by figure 2 is from Locality 83, and those by figures 2a-c are from Locality 83', a slightly 
lower horizon, both in the. Upper Cambrian sandstone near Trempealeau, Trempealeau County, Wisconsin. 
Eoortuis? piaBLo (Walcott) (p. 778). 
Ficure 3. Cast of interior of ventral valve, the type specimen, from Locality 81b, Upper Cambrian sandstone near 
Devils Lake, Sauk County, Wisconsin. U.S. Nat. Mus. Cat. No. 52334a. 
OrusiA SANDBERGI (N. H. Winchell) (p. 769). 
Ficures 4 and 4a. Exterior of ventral valves. U.S. Nat. Mus. Cat. Nos. 35214a and 35214b, respectively. 
4b. Interior of dorsal valve. U.S. Nat. Mus. Cat. No. 35214c. ‘ 
4c and 4d. Interior of the posterior part of a ventral valve. U.S. Nat. Mus. Cat. No. 35214d. 
The specimens represented are all from Locality 302f, Upper Cambrian limestone on north side of Elk Pass, 
Yellowstone National Park, Wyoming. 
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