EXPLANATION OF PLATE X. 



Figs. 1-6. PRODUCTUS INFLATUS McChesney p. Ill 



1-3. Pedicle, posterior and lateral views of a nearly perfect 

 pedicle valve. (W. M., No. 14762.) 



Chester group, Red Bud, Illinois. 



4-6. Pedicle, posterior and lateral views of a nearly perfect pedicle 

 valve. (W. M., No. 14304.) 



Chester group, Meade County, Kentucky. 



Figs. 7-13. PRODUCTUS MESIALIS Hall p. 1 12 



7-9. Pedicle, posterior and lateral views of a pedicle valve. 

 10-12. Similar views of another example. 13. View of a 

 natural impression of a brachial valve. (W. M., No. 14329.) 

 Chert from Keokuk (?) , Pierce City, Missouri. 



Figs. 14-24. PRODUCTUS ALTONENSIS Norwood & Pratten p. 124 



14. Posterior view of a pedicle valve. (W. M., No. 14295.) 



Salem limestone, S per gen Hill, Indiana. 



15. Brachial view of a nearly complete shell. 16-18. Posterior, 

 brachial and lateral views of a nearly complete shell. (W. M., 

 No. 14305.) 



Salem limestone, Harrison County, Indiana. 



19-21. Pedicle, posterior and lateral views of a nearly complete 

 pedicle valve. (W. M., No. 3142.) 



Salem limestone, Washington County, Indiana. 

 22-24. Pedicle, posterior and lateral views of a nearly complete 

 pedicle valve. (W. M., No. 14296.) 



Salem limestone, Spergen Hill, Indiana. 



Figs. 25-27. PRODUCTUS TENUICOSTUS Hall p. 119 



Pedicle, brachial and lateral views of a nearly complete internal 

 cast of a pedicle valve which probably belongs to this species. 

 (W. M., No. 279.) 



Residual chert, Springfield, Missouri. 



