PLATE IV. 
Fig. I. Dalmanella emacerata-filosa. Pedicel valve, enlarged 1.6 diameters. 
Fig. 2. Dalmanella fairmountensis. All figures enlarged about 1. 1 diameters. 
A, B, pedicel valves; C, brachial valve. 
Fig. 3. Plectorthis (Eridorthis) nicklesi. A, C, pedicel valves; B, D, brachial 
valves. 
Fig. 4. Plectorthis (Eridorthis) rogersensis. A, pedicel valve; B, brachial valve. 
Fig. 5. Plectorthis fissicosta, Hall. Type. A, brachial valve; B^ the same en- 
larged 1.6 diameters. 
Fig. 6. Strophomena concordensis. A, interior of pedicel valve; jB, brachial 
valve. 
Fig. 7. Ceraurus miseneri. A, glabella and fixed cheeks; By cephalon. 
Fig. 8. Hehertella alveata. Ay brachial valve; By pedicel valve. 
Fig. 8-C. Hehertella alveata-richmondensis. Brachial valve of a specimen which 
is not the type. 
Fig. 9. Protarea richmondensis. Ay on Strophomena planumhona; By the same 
enlarged 1.6 diameters. 
Fig. 10. Leptcena richmondensis. Ay pedicel valve; By brachial valve. 
Fig. II. Leptcena richmondensis-precursor. Pedicel valve. 
Fig. 12. Rhynchotrema dentata-arnheimensis. Brachial valve. 
Fig. 13. Strophomena maysvillenus. Ay Brachial valve; By pedicel valve. 
Fig. 14. Platystrophia ponderosa. Pedicel valve. 
Fig. 15. Platystrophia ponderosa-auhurnensis. Brachial view. 
Fig. 16. Dalmanella jugosa. Ay pedicel valve; By brachial valve. 
