PLATE XVII—Conlinued- 
Productella exanthemata, Hall. 
Fig. 17. The interior of a brachial valve; showing the cardinal process. 
Hamilton group. Tinker's Falls, N. Y. 
Productella costatula, Hall. 
Figs. 18, 19, 20. Three views of a pedicle-valve. 
Chemung group. Chemung county, N. Y. 
Fig. 35. The interior of a brachial valve. Above the figure is an enlargement of the cardinal process. 
Chemung group. Cattaraugus county, N Y. 
Productella dumosa, Hall. 
Fig. 21. The exterior of a pedicle-valve, showing the rounded costae with numerous spine-bases. 
Hamilton group. Canandaigua lake, N. Y. 
Productella lachrymosa, Conracl, var. lima, Conrad. 
Fig. 22. A view of the pedicle-valve. 
Fig. 23. A pedicle-valve with somewhat more elliptical outline. 
Chemung group. Cattaraugus county, N. Y. 
Productella Boydi, Hall. 
Fig. 24. A pedicle-valve retaining the spines on the cardinal extremities. 
Chemung group. Near ( Philipsburgh ) Belmont, N. Y. 
Productella speciosa, Hall. 
Figs. 25, 26. Two views of the pedicle-valve ; showing the closely-arranged spine-bases. 
Chemung group. Chautauqua county, N. Y. 
Productella striatula, Hall. 
Fig. 27. The exterior of a pedicle-valve. 
Fig. 38. Cardinal view of an internal cast of the pedicle-valve ; showing the mucular scars. 
Fig. 44. An enlargement of the external surface of the shell. 
Chemung group. Chautauqua county, N. Y. 
Productella hirsuta, Hall. 
Fig. 28. A pedicle-valve, retaining spines near the cardinal margin. 
Fig. 39. An enlargement of the cardinal process; showing the divergence of the lobes and the edge of the 
grooves on their posterior face. 
Fig. 45. An enlargement of the external surface. 
Chemung group. 
Fig 
Fig. 
Productella hystricula, Hall. 
!9. The interior of the brachial valve ; showing the cardinal process and the dental sockets. 
50. The exterior of the pedicle-valve; showing the fine, closely crowded spines. 
Chemung group. Chatauqua county, N. Y. 
Productella arcuata, Hall. 
Figs. 31, 32. Two views of a pedicle-valve. 
Yellow sandstones. Burlington, Iowa. 
Productella rarispina, Hall. 
Fig. 33. A pedicle-valve with a few scattered spines. 
Chemung group. Alleghany county, N. Y. 
