EXPLANATION OF PLATE XXIX. 



Figs. 1-13. TETRACAMERA SUBTRIGONA (Meek & Worthen) p. 218 



1-5. Pedicle, brachial, lateral, posterior and anterior views of a 

 large specimen. 6-10. Pedicle, lateral, anterior, posterior and 

 brachial views of a smaller specimen. (W. M., No. 8683.) 

 Keokuk limestone, Warsaiv, Illinois. 



11. View of an internal cast of a pedicle valve. (W. M., No. 8684.) 



Chert of Burlington limestone, Louisiana, Missouri. 



12. View of an internal cast of a brachial valve. (W. M., No. 320.) 



Residual chert, Springfield, Missouri. 



13. View of an internal cast of a pedicle valve with the matrix 

 broken away to show the spondylium. (W. M., No. 13927.) 



Residual chert, Aurora, Missouri. 



Figs. 14-18. RHYNCHOPORA PUSTULOSA (White) p. 230 



Pedicle, brachial, lateral, anterior and posterior views of a very per- 

 fect specimen. (W. M., No. 9690.) 



Kinderhook, Bed No. 4, Burlington, Iowa. 



Figs. 19-30. RHYNCHOPORA HAMBURGENSIS Weller p. 228 



19. View of a pedicle valve. 20-21. Views of two brachial valves. 

 22. Anterior view of an imperfect specimen. 23-26. Pedicle, 

 brachial, lateral and anterior views of a nearly perfect speci- 

 men. 27-30. Similar views of a smaller specimen. (W. M., 

 No. 7742.) 



Hamburg oolite, Kinderhook, Hamburg, Illinois. 



Figs. 31-38. RHYNCHOPORA BEECHERI Greger p. 232 



31-32. Pedicle and posterior views of an internal cast. 33-34. An- 

 terior and pedicle views of an internal cast. 35-36. Brachial 

 and pedicle views of an internal cast. 37-38. Brachial and ped- 

 icle views of an internal cast. (W. M., No. 376.) 

 Residual chert, Springfield, Missouri. 



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