PLATE X— Continued 
Fig. 9. Stropho7nena fluctuosa-occidentalis . A, B, brachial valves, with the con- 
centric wrinkles not well brought out by photography. C, interior of brachial 
valve, the valve strongly tilted so as to show the muscular area, D, E, interiors of 
the pedicel valve. F. W. Sardeson collection. Spring Valley, Minnesota. Rich- 
mond formation. 
Fig. 10. Helicotoma sp. Lateral view of the specimen figured on Plate XI, 
Fig. 4. West of Elkhorn Falls, 3 miles southeast of Richmond, Indiana. 
Elkhorn member. 
Fig. 11. Helicotoma hrocki. Lateral view of the specimen figured on Plate 
XI, Fig. 3. Kagawong, Manitoulin Island. Richmond formation. 
Fig. 12. Clitamhonites multistriata. Partially exfoliated pedicel valve. Half 
a mile north of the railroad station at Danville, Kentucky, Perryville bed. 
Fig. 13. Clitamhonites diversus. Pedicel valve. Ellis Bay. Anticosti. 
Fig. 14. Strophomena millionensis. Brachial valve. An eighth of a mile west 
of the tunnel west of Million, Kentucky. Lower part of Eden. 
Fig. 15. Plectajnbonites curdsvillensis. Brachial valves, interior views. South- 
west of Crow Distillery, Glenn Creek, Woodford county, Kentucky. Curdsville 
bed. 
PLATE XI 
Fig. 1. Strophomena concordensis-huronensis. A, B, C, D, E, interiors of pedi- 
cel valves; F, G, pedicel valves with wrinkles along the hinge line; H, /, brachial 
valves with wrinkles along the hinge-line; K, interior of brachial valve. Clay 
Cliffs, 3 miles north of Wekwemikongsing, east end of Manitoulin Island. 
Richmond group. 
Fig. 2. Strophomena sulcata. A, brachial valve. B, pedicel valve. Kaga- 
wong, Manitoulin Island. Richmond group. 
Fig. 3. Helicotoma hrocki. Kagawong, Manitoulin Island. Richmond group. 
See also Plate X, Fig. 11. 
Fig. 4. Helicotoma sp. West of Elkhorn Falls, 3 miles southeast of Richmond, 
Indiana. Elkhorn member of the Richmond. See also Plate X, Fig. 10. 
Fig. 5. Orthorhynchula linneyi. Brachial valve, with beak of pedicel valve 
showing above it. Four miles north of Versailles, Kentucky, Perryville bed. 
Fig. 6. Strophomena planumhona-gerontica. Lateral view, showing convexity 
and obesity of brachial valve. Hillside west of Gore Bay, Manitoulin Island. 
Richmond group. 
Fig. 7. Strophomena incurvata. Pedicel valve, interior view. High Bridge, Ken- 
tucky. Tyrone member of High Bridge limestone. 
Fig. 8. Strophomena 7iutans. Fragment of pedicel valve, interior view. Clay 
Cliffs, 3 miles north of Wekwemikongsing, Manitoulin Island. Richmond for- 
mation. 
Fig. 9. Strophomeyia incurvata. A, brachial valve; B, pedicel valve, interior 
view; C, brachial valve, interior view. A, LaCloche Island; B, C, Goat Island; 
both northeast of Manitoulin Island. Black River formation. 
Fig. 10. Strophomena neglecta. Pedicel valve, interior view. Kagawong, Mani- 
toulin Island. Richmond group. 
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