PLATE XVU— Continued- 



Pkoductella exanthemata, Hall. 



Fig. 17. The inteiior of a brachial valve ; showiiifj the ravdinal process. 

 Hamilton gi^oiip. Tinker's J^alls, iV. Y. 



Pkoductella costatula, Hail. 



Figs. 18, 19, 20. Three views of a j)eilicle-valve. 



Chemung group. C/ieinung county, N. Y. 

 Fig. 35. The interior of a brai'.hial valve. Above the figure is an enlargement of the cardinal process. 



Chemung group. Cattaraugtis cmmty, N. Y. 



Pkoductella dumosa, Hall, 



Fig. 21. The exterior of a pedicle-valve, showing the rounded cost;e with numerous spine-bases. 

 Hamilton group. Canandaigua lake, N. Y. 



Pkoductella lachrymosa, C'oiu;ui, 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. 



Pkoductella Boydi, Hall. 



Fig. 24. A pedicle-valve retaining the sjiines on the cardinal exti-emities. 



Chemung group. Near (Philipsbiirgh) Belmont, N. Y. 



Pkoductella speciosa, Hall. 



Figs. 25, 26. Two views of the pedicle-valve ; showing the closely-arranged spiue-biises. 

 Chemung group. Chautauqua cmmty, N. Y. 



Pkoductella striatula, Hall. 



Fig. 27. The exterior of a pedicle-valve. 



Fig. 38. Cardinal view of an internal cast of the pedicV-valve ; showing the mncular scars. 



Fig. 44. An enlargement of the external surface of the sliell. 



Chemung group. Chautauqua convty, N. Y. 



Pkoductella hiksuta, 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 an<l the edge of the 



grooves on their posterior face. 

 Fig. 45. An enlargement of the external surface. 



Chemung group. Meadville, Pennsylvania. 



Pkoductella hystricula, Hall. 



Fig 29. The interior of the brachial valve ; showing the cardinal process and the dental sockets. X 2. 

 Fig. 30. The exterior of the pedicle-valve ; showing the fine, closely crowded spines. 

 Chemung group. Chatauqua county, N. Y. 



Pkoductella arcuata, Hall. 



Figs. 31, 32. Two views of a pedicle-valve. 



Yellow sandstones. Burlington, Iowa. 



Pkoductella kakispina, Hall. 



Fig. 33. A pedicle-valve with a few scattered spines. 



Chemung group. Alleghany county, N. Y. 



