PLATE X. 39 
OxsoLus MHRA (Hall and Whitfield)—Continued. 
Figure 2d. Exfoliated ventral valve from Locality 61, Upper Cambrian Dunderberg shale, south of the Hamburg 
; mine, Eureka district, Nevada, showing outline of visceral area. U.S. Nat. Mus. Cat. No. 5156la. 
2e. Partly exfoliated ventral valve, showing radial striation of interior layers of the shell, Locality 58, 
Middle Cambrian Secret Canyon shale, New York and Secret canyons, Eureka district, Nevada. 
U.S. Nat. Mus. Cat. No. 51560a. 
Oxsoius ANcCEPS Walcott (p. 380). 
Ficure 3. Partly exfoliated ventral valve. U.S. Nat. Mus. Cat. No. 27302a. 
3a. Partly exfoliated ventral valve showing the area. U.S. Nat. Mus. Cat. No. 27302b. 
3b. Cast of the interior of a dorsal valve, the type specimen, showing the area and traces of the vascular 
markings. U.S. Nat. Mus. Cat. No. 27302c. 
3c. More elongated dorsal valve than that represented by figure 3b. U.S. Nat. Mus. Cat. No. 27302d. 
The specimens represented in figures 3, 3a-c are all from Locality 68, Lower Ordovician Pogonip limestone, north- 
east of Adams Hill, Eureka district, Nevada. 
Fieure 3d. Ventral valve. U.S. Nat. Mus. Cat. No. 51541a. 
3e. Partly exfoliated dorsal valve showing interior layers of the shell. U.S. Nat. Mus. Cat. No. 51541b. 
3f. Exterior of dorsal valve. U.S. Nat. Mus. Cat. No. 51541c. 
The specimens represented in figures 3d-f are from Locality 61, Upper Cambrian Dunderberg shale, south of the 
Hamburg mine, Eureka district, Nevada. 
Oxpotws sp. undt. a Walcott (p. 422). 
Figure 4. Ventral valve compressed in shaly limestone of Locality 338v, Lower Ordovician, 1 mile southwest of 
Middle Granville, Washington County, New York. U.S. Nat. Mus. Cat. No. 51652a 
