EXPLANATION OF PLATE XV. 



Figs. 1-8. PRODUCTUS MAGNUS Meek & Worthen p. 117 



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

 pedicle valve. 4. View of a natural mould of the exterior of 

 brachial valve. (W. M., No. 14321.) 5. Posterior view of 

 another example showing the arrangement of spine bases along 

 the cardinal margin. (W. M., No. 14765.) 



Keokuk, Monroe County, Illinois. 



6-8. Pedicle, lateral and posterior views of a smaller example, 

 having the characters of the shell described as P. fcutoncnsis 

 by Shumard. (W. M., No. 14308.) 



Keokuk, Fenton, St. Louis County, Missouri. 



36 



