PLATE LXIII. Adit} 
JTIELMERSENIA LADOGENSIS (Jeremejew) (p. 368). 
Fieure 7, Exterior view and side outline of a ventral valve from Locality 336p, Upper Cambrian sandstone at Kunitz, 
Pskow, Russia. U.S. Nat. Mus. Cat. No. 51941a. 
7a. Exterior of a transverse dorsal valve from Locality 3360, Upper Cambrian sandstone at Koporje, St. Peters- 
burg, Russia. U.S. Nat. Mus. Cat. No. 51940a. 
7b and 7b’. Exterior of a rounded ventral valve, and side outline, associated with the specimen represented 
by figure 7a. U.S. Nat. Mus. Cat. No. 51940b. 
7c. Posterior view of a dorsal valve from Locality 336g, Upper Cambrian sandstone near Ladoga, Government 
of St. Petersburg, Russia. Copied from Pander [1861, Pl. IT, fig. 2f] 
7d. Interior view of a ventral valve, the type specimen, associated with the valve represented by figure 7c. 
Copied from Pander [1861, Pl. II, fig. 2d]. 
7e. Exterior of a dorsal? valve associated with the specimen represented by figure 7a. U.S. Nat. Mus. Cat. 
No. 51940c. 
7f. Interior of a ventral ? valve associated with the specimen represented by figure 7a. U.S. Nat. Mus. Cat. 
No. 51940d. 
Osotts (WeEsTONIA) ELONGATUS Walcott (p. 459). 
Figure 8. Compressed, exfoliated ventral valve. U.S. Nat. Mus. Cat. No. 51722b. 
8a. Exfoliated interior of a ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 51722a. Copied 
from Walcott [1908d, Pl. VII, fig. 12]. 
8b and 8c. Exfoliated interiors of dorsal valves. U.S. Nat. Mus. Cat. Nos. 51722c and 51722d, respectively. 
8d. Enlargement of a portion of the matrix of the outer surface of the dorsal valve represented by figure 8b. 
The spaces inclosed by the oblique lines are not so convex as represented on the figure. U.S. Nat. 
Mus. Cat. No. 51722c. 
The specimens represented are all from Locality 105x, Middle Ordovician shales in Wasatch Canyon, north ‘of 
Brigham, Boxelder County, Utah. 
OxsoLus (WesTonIA) NoTcHENSIS Walcott (p. 463). 
Ficure 9. Fragment of a ventral valve, the type specimen, preserving a portion of the outer surface, from Locality 
105t, Lower Ordovician limestone on Notch Peak, House Rangé, Utah. U.S. Nat. Mus. Cat. 
No. 5173la. Copied from Walcott [1908d, Pl. VII, fig. 13]. 
OxsoLus (ForprinrA) PERFECTUS Walcott (p. 429). 
Ficures 10 and 10’. Exterior and side view of a ventral valve. U.S. Nat. Mus. Cat. No. 51947b. 
10a. Interior of a ventral valve, the type specimen. U.S. Nat. Mus. Cat. No. 51947a. Copied from 
Walcott [1908d, Pl. Vil, fig. 16]. 
10b. Exterior and side view of a dorsal valve. U.S. Nat. Mus. Cat. No. 51947c. 
10c and 10d. Interiors of dorsal valves. U.8..Nat. Mus. Cat. Nos. 51947d and 51947e, respectively. 
The specimens represented are all from Locality 30n, Middle Cambrian Weeks limestone, in Weeks Canyon, 
House Range, Utah. 
