PLATE 10 



Pigs. Cyclocoelia sordida (Hall) 



1, 5. — Ventral and dorsal exteriors. 



2, 4.- — Ventral and dorsal internal molds, the former show- 



ing short dental plates and the latter the mold of the 

 median septum. 



Ordovician (Maysville, Fairmount), Cincinnati, 



Ohio. Cat. No. S 383. x 2. 



Cycloccelia sectistriata (Ulrich) 



3, 7, 9. — Lateral, dorsal, and ventral views of exterior. 



Ordovician (Maysville, Fairmount), Cincinnati, 

 Ohio. Cat. No. S 387 (one of Ulrich's type lot). 

 x2. 



Skenidioides billingsi Schuchert and Cooper 



6, 11, 13, 14. — Lateral, ventral, posterior, and dorsal views 



of holotype. 

 8, 10, 12. — Dorsal interiors of paratypes, illustrating well 

 high dorsal septum, cardinal process, and cruralium. 

 Fulcral plates visible forming sockets. Brachiophores 

 broken off, but when preserved, very long. 

 Ordovician (Black River), Paquette Rapids, Ottawa 

 River, Quebec. Cat. No. S 20 13 (holotype, 2013a). 

 x4. 



Dinorthis (Plaesiomys) subquadrata (Hall) 



15. — Ventral internal mold, showing characteristic muscle- 

 scars. The adjustor scars are prominent in the whole 

 dinorthid stock. 

 Ordovician (Richmond), Spring Valley, Minn. Cat. 

 No. S 732. X 1.5. 

 17, 18. — Dorsal and ventral exteriors, x 1. 

 24. — Ventral interior, showing musculature and course of 

 pallial markings, x 1.5. 

 Ordovician (Richmond), Richmond, Ind. Cat. 

 No. S728. 



Figs. Dinorthis (Plaesiomys) subquadrata (Hall) — Cont. 



25. — Dorsal interior, showing cardinalia. x 1.5. 

 26. — Interior of a gerontic ventral valve, showing extreme 

 thickening of shell, x 1.5. 



Ordovician (Richmond), Richmond, Ind. Cat. 



No. S728. 



Valcourea magna Schuchert and Cooper, n. sp. 

 16, 20, 27, 29. — Posterior, lateral, dorsal, and ventral views 



of exterior. 



28. — Ventral interior, showing musculature and pallial 



markings. This specimen is not provided with a del- 



tidium but the pedicle callist is visible. 



Ordovician (Simpson). Criner Hills, Okla., sect. 



35, 6 S, 1 E. Cotypes. Cat. No. S 779. x 1.5. 



Valcourea deflecta (Conrad) 



19. — ^Ventral interior, showing muscle-scars and deltidium 



in place. 

 21. — Dorsal interior, showing cardinalia. Notothyrial 



platform greatly thickened. 

 23. — Interarea of specimen shown in fig. 19, showing del- 

 tidium, and teeth with accessory sockets. 

 Ordovician (Black River), Allen Hunter quarry. 

 Fountain, Minn. Cat. No. S 771. x 1.5. 



Valcourea loricula (Hall and Clarke) 



22. — Ventral interior, showing musculature and lateral 

 ovarian impressions. This specimen is not provided 

 with a deltidium but in its place is a decided callist. 

 This suggests that the deltidium, when present in 

 Valcourea at least, is the seat of pedicle attachment. 

 Ordovician (Black River), Allen Hunter quarry, 

 Fountain, Minn. Cat. No. S 771a. x 1.5. 



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