PLATE CI. v09 
NisusiA (JAMESELLA) AMiII Walcott (p. 731). 
Figures 6, 6a, and 6b. Top, side, and back views of the type specimen, a ventral valve from Locality 56a, Lower 
Cambrian limestone bowlder in Sillery conglomerate on the south shore of the St. Lawrence, 4 miles 
(6.4 km.) below Quebec, Canada. U.S. Nat. Mus. Cat. No. 52296. 
OrusIA? EUREKENSIS (Walcott) (p. 765). 
Ficures 7, 7’, and 7’. Top, posterior, and side views of part of mold of the interior of a ventral valve, the type 
specimen. U.S. Nat. Mus. Cat. No. 24596a. 
7a, 7a’, and 7a’”. Top, posterior, and side views of a mold of the interior of a dorsal valve. U.S. Nat. Mus. 
Cat. No. 24596b. 
The specimens represented are both from Locality 55b, Middle Cambrian, top of Eldorado limestone on west side 
of Secret Canyon, Eureka district, Nevada. The figures (7 and 7a) are redrawn from the specimens illustrated by 
Walcott [1884b, Pl. EX, figs. 8a and 8, respectively]. 
BILLINGSELLA DICE Walcott (p. 754). 
Ficurss 8, 8’, and 8a. Casts of the interior of two ventral valves, with side view. U. S. Nat. Mus. Cat. Nos. 52248 
and 52248b, respectively. Figure 8 represents the type specimen. 
8b. Partial posterior view of the matrix of a distorted ventral valve. U.S. Nat. Mus. Cat. No. 52248c. 
8c. Matrix of a distorted dorsal valve. U.S. Nat. Mus. Cat. No. 52248d. 
Sd. Cast of the interior of a distorted dorsal valve. U.S. Nat. Mus. Cat. No. 52248e. 
The specimens represented are all from Locality 319f, Lower Ordovician drift bowlder of sandstone found near 
St. Albans, Vermont. 
Nisusta (JAMESELLA) ARGENTA Walcott (p. 731). 
Figure 9. Top and side view of the type specimen, a ventral valve from Locality 1p, limestones of No. 2 of the Silver 
Peak group, about 2.5 miles south of Barrel Spring, Silver Peak quadrangle, Nevada. U.S. Nat. Mus. 
Cat. No. 52297a. 
9’. Posterior view of another ventral valve. The specimen from which this was drawn can not be located. 
Ja and 9a’. Top and side views of a ventral valve from Locality 1m, limestones of No. 2 of the Silver Peak 
group, about 2.5 miles south of Barrel Spring, Silver Peak quadrangle, Nevada. 
9b and 9b’. Top and side views of a dorsal valve. U.S. Nat. Mus. Cat. No. 52298b. 
Nisusta (JAMESELLA) UTAHENSIS Walcott (p. 737). 
Ficures 10 and 10a. Top and side views of the type specimen, from Locality 7w, Middle Cambrian limestone in Rock 
Canyon, in the Wasatch Mountains, east of Provo, Utah County, Utah. 52305 q@ 
