EXPLANATION OF PLATE LVII. 



Figs. 1-3. SPIRIFER LOGANI Hall p. 363 



1-2. Posterior and lateral views of the specimen illustrated on 

 Plate LVI. 3. View of the interior of the pedicle valve of 

 the same specimen. (W. M., No. 6579.) 

 Kcokuk limestone, Keokuk, Iowa. 



Figs. 4-11. BRACHYTHYRIS CHOUTEAUENSIS Weller p. 373 



4-7. Pedicle, brachial, posterior and lateral views of a nearly 

 complete specimen. (W. M., No. 8544.) 



Pierson limestone, near Springfield, Missouri. 

 8-10. Lateral, pedicle and brachial views of a nearly complete 

 specimen. Holotype. (W. M., No. 9664.) 



Chouteau limestone, Choutcau Springs, Missouri. 

 11. Brachial view of a somewhat crushed specimen. (W. M., 

 No. 13536.) 



Fern Glen formation, Fern Glen, Missouri. 



Fig. 12. BRACHYTHYRIS PECULIARIS ( Shumard ) p. 381 



View of a broad pedicle valve. (W. M., No. 9722.) 

 Chouteau limestone, Pettis County, Missouri. 



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