PLATE XV. 57 
OBoLus? sp. undt. e Kayser (p. 423). 
Figure 8. Ventral valve associated with Hoorthis saltensis in Locality 389b, Upper Cambrian sandstone at Tilcuya, 
Province of Jujuy, Argentina. Copied from Kayser [1876, Pl. I, fig. 14]. 
Oso us? sp. undt. f Kayser (p. 423). 
Figure 9. Several valves on small fragment of limestone from Locality 332, Upper Cambrian at Saimaki, Liaotung, 
China. Copied from Kayser [1883, Pl. III, fig. 2]. 
Oxo us? BAvARICUS (Barrande) (p. 385). 
Ficure 10. Ventral valve, the type specimen, from Locality 303c, passage beds between the Cambrian and Ordo- 
vician, suburbs of Hof, Bavaria, Germany. Copied from Barrande [1868a, fig. 62], who described 
it as Lingula bavarica. 
10a. Dorsal valve associated with the shell represented by figure 10 in Locality 303ce. Copied from Barrande 
[1868a, fig. 64], who described it as Obolus? palliatus. 
Oxso.us scumiptr Mickwitz (p. 412). 
Figures lla-c. Exterior, side, and interior views of a dorsal valve, the type specimen, from Locality 395, Upper 
Cambrian Obolus sandstone at Joa, near Jegelecht, Esthonia, Russia. Copied from Mickwitz [1896, 
Pl. II, figs. 14a-c]. 
OxsoLus? MurRAyYI Billings (p. 405). 
Figure 12. Figure of the original type specimen from Locality 314g, Lower Ordovician, Maiden Arm, Hare Bay, 
northern Newfoundland. Geol. Survey Canada. The specimen is the one on which Billings [1865, 
p. 362] based his species, but he did not figure it. : 
