EXPLANATION OF PLATE XVI. 



Figs. 1-15. PRODUCTUS OVATUS Hall p. 132 



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

 pedicle valve. (Productus pileiformis.) (W. M., No. 14323.) 



Chester group, Chester, Illinois. 



4-5. Pedicle and lateral views of a pedicle valve. 6-7. Direct 

 and profile views of the external impression of a brachial valve. 

 (Productus pileiformis.) (W. M., No. 14314.) 



Chester group, Meade County, Kentucky. 



8-9. Pedicle and lateral views of a nearly complete pedicle 

 valve. (W. M., No. 326.) 



Keokuk limestone, near Springfield, Missouri. 



10-11. Pedicle and lateral views of a nearly complete pedicle 

 valve. (W. M., No. 10130.) 



St. Louis limestone, St. Louis, Missouri. 



12. Direct view of an incomplete pedicle valve. (Productus Iccvi- 

 costus WhiteJ (W. M., No. 6714.) 



Kinderhook, bed No. 7, Burlington, Iowa. 



13. Direct view of a pedicle valve. (Productus l&vicostus White) 

 (W. M., No. 5924.) 



Chonopectus limestone, Burlington, Iowa. 



14-15. Brachial and pedicle views of an incomplete specimen 

 preserving both valves. (Productus la-z'icostus White) 

 (W. M., No. 296.) 



Lower Burlington limestone, near Springfield, Missouri. 



Figs. 16-22. PRODUCTUS PARVUS (Meek and Worthen) p. 121 



16-19. Pedicle, brachial, lateral and posterior views of a very 

 perfect shell. (W. M., No. 9915.) 



Chester group, Chester, Illinois. 



20-22. Posterior, lateral and pedicle views of another perfect 

 specimen. (W. M., No. 10923.) 

 Pella beds, Pella, Iowa. 



