Explanation of Plate 11 



Figs. 1-4 Polytylites tricollinus (Jones and KIrkby). Dorsum, left valve, venter and pos- 

 terior end, x30. Glen Dean formation, loc. 1 p. 54 



5 Polytylites trilobus (Croneis and Gale). Left valve, x30. Golconda formation, loc. 16 p. 54 



6,17 Polytylites superus (Croneis and Gale). 6 left valve, Menard formation, loc. 7; 



17 right valve, Golconda formation, loc. 16; x30 p. 53 



7-9 Savagella? acuminata Cooper, n. sp. Posterior end, dorsum, and right valve. 



Holotype, x30. Renault formation, loc. 12 p. 47 



10-12 Chesterella exuta Croneis and Gutke. Dorsum, left valve and posterior end, x30. 

 Renault formation, loc. 25 



13-14 Deloia tumida Cooper, n. sp. Dorsum and left valve, somewhat crushed. Holotype, 



x30. Kinkaid formation, loc. 3 . . . v p. 54 



15-16 Jonesina equilatera Cooper, n. sp. Dorsum and left valve. Holotype, x20. Paint 



Creek formation, loc. 2 p. 56 



18 Deloia spinosa Croneis and Bristol. Left valve, x30. Vienna formation, loc. 10 . . p. 54 



19-21 Chesterella fissurata Croneis and Gutke. Dorsum, left valve and posterior end, x30. 

 Renault formation, loc. 9 



22-23 Polytylites nvilsoni (Croneis and Gutke). Dorsum and left valve, x30. Renault 



formation, loc. 9 p. 54 



24 Polytylites suhlineatus (Croneis and Thurman). Left valve, x20. Kinkaid forma- 

 tion, loc. 5 p. 53 



25-27 Geffenina marmerae Coryell and Sohn. Anterior end, dorsum and left valve, x30. 

 Reynolds formation, loc. 35 



28-30 Chesterella incerta Cooper, n. sp. Dorsum, left valve and posterior end. Holotype, 



x40. Renault formation, loc. 25 p. 54 



31-33 Geffenina johnsoni Coryell and Sohn. Dorsum, left valve and posterior end, x30. 

 Reynolds formation, loc. 35 



34 Denisonia cirrata Cooper, n. sp. Right valve. Holotype, x30. Golconda formation, 



loc. 18 p. 55 



35 Deloia serrata Croneis and Thurman. Left valve, x30. Kinkaid formation, loc. 3 



36-39 Jonesina craterigera (Brady). 36-37 Dorsum and left valve of female, x30; Gol- 

 conda formation, loc. 19; 38-39 dorsum and left valve of male, x40. Glen Dean 

 formation, loc. 1. Note difference in magnification p. 56 



40-41 Denisonia hrevicosta Cooper, n. sp. Dorsum and left valve. Holotype, x30. Gol- 

 conda formation, loc. 22 p. 54 



42-44 Geffenina? praelonga Cooper, n. sp. Dorsum, left valve and posterior end. Holo- 

 type, x30. Golconda formation, loc. 19 p. 55 



45 Denisonia cincta Croneis and Bristol. Left valve, broken and somewhat crushed, x30. 



Clore formation, loc. 4 



46-48 Deloia sulcata Croneis and Funkhouser. Posterior end, dorsum and right valve, x30. 

 Golconda formation, loc. 17 



[88 



