PLATE XCI. 
b. Dental sockets. d’. Cast of umbonal cavity. 
ce. Crura. j. Cardinal process. 
Eoorruis rEmMNicHA (N. H. Winchell) (p. 786). 
[Text fig. 7, p. 299, and Pl. XCIH, figs. 2, 2a-d, 3, 3a-e.] 
Fieures 1, la, and 1b. Casts, taken in a natural mold, of ventral valves in which the coste and mesial sinus show 
wide variation in form. U.S. Nat. Mus. Cat. Nos. 52361a, 52361b, and 52361c, respectively. 
le. Top view, with side and back outlines, of a natural cast of part of the interior of a ventral valve. The 
tripartite division of the interior of the shell (visceral area) opposite the deltidium is finely shown. 
U.S. Nat. Mus. Cat. No. 52361d. 
1d. Natural cast of the interior of a ventral valve, with strong rounded coste. U.S. Nat. Mus. Cat. No. 
52361e.: 
le. Natural cast of the interior of a ventral valve, with fine coste and short auriculate extension of the cardinal 
angles. U.S. Nat. Mus. Cat. No. 52361f. 
lfand lg. Natural casts of small finely costate ventral valves, with slightly auriculate cardinal angles. U.S. 
Nat. Mus. Cat. Nos. 52361g and 52361h, respectively. 
lh. Natural cast of strongly costate ventral valve, with short cardinal line. Locality 80a, Upper Cambrian 
“St. Croix sandstone ’’ 4 miles (6.4 km.) north of Reedsburg, Sauk County, Wisconsin. U.S. Nat. Mus. 
Cat. No. 52362a. 
li. Cast in natural mold of a ventral valve, with short cardinal line, strong costee, and median sinus. U. 8. 
Nat. Mus. Cat. No. 52361i. 
1j. Natural cast of a small ventral valve, with very strong coste. U.S. Nat. Mus. Cat. No. 52361). 
1k. Natural cast of a ventral valve, with fine costz interspaced between strong coste. U.S. Nat. Mus. Cat. 
No. 52361k. : 
11. Natural cast of a ventral valye, with strong costz much like those of figure 1d. A gradation of the strength 
of the cost is noticeable from figure 11 through figures 1d, 1j, 1b, 1c, 1h, 1f, and 1g. The specimen 
represented by figure 11 is associated with the ventral valve shown in figure lh. U.S. Nat. Mus. 
Cat. No. 52362b. 
1m, In, lo, Ip, and 1q. Natural casts of dorsal valves, showing variation in form and strength of surface coste. 
U.S. Nat. Mus. Cat. Nos. 52361 1-p, respectively. 
lr. Enlargement of the posterior portion of figure lq. U.S. Nat. Mus. Cat. No. 52361p. 
1s. Enlargement of the surface of a ventral valve from Locality 12n, Upper Cambrian limestone of the Reagan 
sandstone, sec. 1, T. 28.,R.1 E., Ardmore quadrangle (U. 8. Geol. Survey), Carter County, Okla- 
homa. U.S. Nat. Mus. Cat. No. 52356a. 
With the exception of figures 1h, 11, and 1s the specimens represented are all from Locality 97a, Upper Cambrian 
“St. Croix sandstone ’’ near Winfield, Jefferson County, Wisconsin. i 
EoorTHIS REMNICHA WINFIELDENSIS (Walcott) (p. 788). 
Ficure 2. Exterior and side views of a cast in a natural mold of the exterior surface of a ventral valve, the type 
specimen. U.S. Nat. Mus. Cat. No. 52374a. 
2a, 2b, and 2c. Three natural casts of ventral valves that illustrate variation in form. U.S. Nat. Mus. Cat. 
Nos. 52374b, 52374c, and 52374d, respectively. 
2d. Exterior and side views of natural cast of exterior of dorsal valve. U.S. Nat. Mus. Cat. No. 52374e. 
2e. Exterior, side, and back views of natural cast of a dorsal valve. U.S. Nat. Mus. Cat. No. 52374f. 
The specimens represented are all from Locality 97a, Upper Cambrian “St. Croix sandstone’? near Winfield, 
Jefferson County, Wisconsin. 
Eoortuis inprnest (Walcott) (p. 780). 
Ficure 3. Ventral valve. The outline is partly restored from another shell. U.S. Nat. Mus. Cat. No. 52340a. 
Type specimen figured by Walcott [1899, Pl. LXII, fig. la] as Eoorthis remnicha. 
3a. A small dorsal valve. U.S. Nat. Mus. Cat. No. 52340b. Specimen figured by Walcott [1899, Pl. LXII, 
fig. 1b] as Hoorthis remnicha. 
3b. Interior'of a ventral valve. U.S. Nat. Mus. Cat. No. 52340c. 
The specimens represented are all from Locality 302c, Upper Cambrian shaly limestone on south side of Gallatin 
Valley, Yellowstone National Park, Wyoming. 
Eoortuis PAPias (Walcott) (p. 785). 
Ficure 4. Top and side views of the type and only specimen of the species in the collection. Locality 61, Middle 
Cambrian shales near the top of No. 6 of the Manuels Brook section [ Walcott, 1891b, p. 261], east side 
of Manuels Brook, Conception Bay, Newfoundland. U.S. Nat. Mus. Cat. No. 52353a. 
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