EXPLANATION OF PLATE LXXXIII. 



Figs. 1-2. SPIRIFER FORBESI Norwood and Pratten p. 331 



Views of two separate brachial valves. (W. M., Nos. 5654 and 

 13531.) 



Burlington limestone, Springfield, Missouri, and Burling- 

 ton, Iowa. 



Figs. 3-5. BRACHYTHYRIS PECULIARIS (Shumard) p. 381 



Pedicle, brachial and lateral views of a very perfect specimen. 

 (W. M., No. 14780.) 



Chouteau limestone, Calhoun County, Illinois. 



Fig. 6. BRACHYTHYRIS BURLINGTONENSIS n. sp p. 371 



Brachial view of an internal cast. (W. M., No. 7501.) 

 Kinder hook, Bed No. 5, Burlington, Iowa. 



Figs. 7-8. RHIPIDOMELLA BURLINGTONENSIS (Hall) p. 149 



Interior views of the pedicle and brachial valves of one individual. 

 (W. M., No. 7858.) 



Burlington limestone, Burlington, loiva. 



Figs. 9-10. RHIPIDOMELLA DUBIA (Hall) p. 160 



Interior views of a pedicle and a brachial valve. (W. M., Nos. 

 7846 and 11927.) 



Salem limestone, Colesburg, Kentucky, and Spergen Hill, 

 Indiana. 



Fig. 11. SCHELLWIENELLA INFLATA (White and Whitfield) . p. 59 



View of an internal cast of a pedicle valve. (W. M., No. 14759.) 

 Kinderhook, Bed No. 7, Burlington, Iowa. 



Figs. 12-13. PRODUCTUS INDIANENSIS Hall p. 131 



Pedicle and lateral views of the holotype. (A. M. N. H., No. 5087) 

 Salem limestone, Spergen Hill, Indiana. 



Figs. 14-17 PRODUCTUS MESIALIS Hall p. 112 



14-16. Pedicle, posterior and lateral views of a pedicle valve. 17. 

 View of an impression of the exterior of a brachial valve. Co- 

 types. (A. M. N. H., No. 5090.) 



Keokuk limestone, Nauvoo, Illinois. 



Figs. 18-20. PRODUCTELLA SUBL^VIS n. sp p. 102 



18-19. Views of the more or less modified internal casts of two 

 pedicle valves. 20. View of an incomplete external impression 

 of a brachial valve. (W. M., No. 10558.) 



Kinderhook sandstone, Kinderhook, Illinois. 



Figs. 21-22. CHONOPECTUS FISCHERI (Norwood and Pratten) p. 96 



21. View of the internal cast of a large pedicle valve. 22. View 

 of an impression of the pedicle valve showing the cardinal 

 spines. (W. M., No. 14779.) 



Chonopectus sandstone, Burlington, lozva. 



186 



