EXPLANATION OF PLATE VI. 



Figs. 1-14. ORTHOTETES KASKASKIENSIS McChesney p. 77 



1-4. Pedicle, brachial, lateral and posterior views of a nearly com- 

 plete specimen. 5-8. Pedicle, brachial, posterior and lateral 

 views of a smaller example. (W. M., No. 10920.) 



Pella beds, Pella, Iowa. 



13-14. Pedicle and brachial views of a nearly complete example. 

 (VV. M., No. 8647.) 



Chester group, Meade County, Kentucky. 



9-12. Brachial, pedicle, posterior and lateral views of a nearly com- 

 plete specimen. (W. M., No. 8648.) 



Chester group, Randolph County, Illinois. 



Fig. 15. ORTHOTETES KASKASKIENSIS McChesney (?) p. 77 



View of a nearly complete but exfoliated brachial valve which differs 

 from the more typical representatives of the species in having 

 much stronger costae at regular intervals. (W. M., 14760.) 

 Chester group, Red Bud, Illinois. 



Figs. 16-21. STREPTORHYNCHUS MINUTUM Cumings p. 70 



16-18. Pedicle, brachial and posterior views of a complete example 

 (x4). 19-21. Similar views of another example (x4). (W. M.) 

 Salem limestone, Bloomington, Indiana. 



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