PLATE LXXXIX. 
cf. Cardinal muscle scar. j. Anterior lateral muscle scar. 
d. Delthyrium. vs. Vascular sinus. 
h. Central muscle scar. 
BILLINGSELLA RICHTHOFENI Walcott (p. 761). 
Ficure 1. Exterior of ventral valve, the type specimen, with side outline, from Locality C3, Lower Cambrian Manto 
; shale, 2.5 miles (4 km.) southwest of Yenchuang, Sintai district, Shantung, China. U. 8. Nat. 
Mus. Cat. No. 52559a. 
WIMANELLA SIMPLEX Walcott. (p. 748). 
[Text fig. 64, p. 748.] 
Fieure 2. Ventral valve from Locality 4v, Lower Cambrian shale on Gordon Creek, 6 miles (9.6 km.) from the South 
Fork of the Flathead River, Ovando quadrangle (U. 8. Geol. Survey), Powell County, Montana. 
U. S. Nat. Mus. Cat. No. 52278a. Copied from Walcott [1908d, Pl. X, fig. 2]. This is the type 
specimen. 
2a, 2b, and 2c. Ventral valves of varying outlines owing to distortion in the shales of Locality 4w, Lower 
Cambrian shales on Youngs Creek, about 5 miles (8 km.) from its junction with Danaher Creek, 
Ovando quadrangle (U. 8. Geol. Survey), Powell County, Montana. U. 8S. Nat. Mus. Cat. Nos. 
52277a-c, respectively. 
2d. Cast of interior of ventral valve associated with the specimens represented by figures 2a-c. U.S. Nat. 
Mus. Cat. No. 52277d. 
2e. Ventral and dorsal valves compressed and resting against each other at the posterior margins, associated 
with the specimen represented by figure 2. U.S. Nat. Mus. Cat. No. 52278b. 
Orusta uraHENsIS Walcott (p. 770). 
Ficure 3. Transverse dorsal valve, the type specimen. U.S. Nat. Mus. Cat. No. 52281a. 
3a. Ventral valve with rounded cardinal angles. U.S. Nat. Mus. Cat. No. 52281b. 
3b. Fragment of a dorsal valve. U.S. Nat. Mus. Cat. No. 52281c. 
3c. Enlargement of outer surface. U: 8. Nat. Mus. Cat. No. 52281d. 
The specimens represented are from Locality 33r, Middle Cambrian limestone in canyon about 1 mile (1.6 km.) 
east of Cricket Spring, Cricket Range (locally known as the Beaver River Range or the Beaver Mountains), northwest 
of Black Rock, Millard County, Utah. 
WynNNIA WarTHt (Waagen) (p. 771). 
[Text figs. 68A and 684’, p. 771.) 
Fieure 4. Cast of the interior of the ventral valve represented by figure 4b, showing faint muscle area and strong 
vascular sinuses. This figure is incorrect and is superseded by text figure 68A, page 771, which see. 
Geol. Survey India Cat. No. 4/124. The area of this specimen was figured by Waagen [1891, Pl. 
II, fig. 14). 
4a. Cast of the interior of another ventral valve showing faint muscle area and strong vascular sinus. Geol. 
Survey India Cat. No. 4/122. Type specimen figured by Waagen [1891, Pl. I, figs. 12a—b]. 
4b. Area of the specimen represented by figure 4. The small deltidium represented in the drawing is a mis- 
take; there is none on the specimen. The delthyrium is much too large in the drawing owing to the 
breaking away of the point of the beak. The specimen is correctly represented in text figure 68A’, 
page 771, which see. Geol. Survey India Cat. No. 4/124. Specimen figured in this position by 
Waagen [1891, Pl. II, fig. 14]. 
4c. Cast of the interior of a dorsal valve. This valve is fitted in its proper place to the ventral valve repre- 
sented by figure 4a, and the two valves probably belong to the same specimen. Geol. Survey India 
Cat. No. 4/122. 
4d, 4e, and 4f. Diagrammatic figures of a very young individual showing the two valves united. Copied 
from Waagen [1891, Pl. II, figs. 2a-c]. 
The specimens represented are all from Locality 357d, Middle Cambrian concretionary shales of the Khussak 
group at several localities between Chél Hill and Kiura (Khewra), eastern part of the Salt Range, India. The speci- 
mens represented by figures 4 and 4a likely occur in the vicinity of Chél Hill. They are all in the collection of the 
Geological Survey of India. 
298 
