PLATE XVII— Con tinned • 



Pkoductella exanthemata, Hall. 



Fig. 17. The interior of a brachial valve ; showing the cardinal process. 

 Hamilton group. Tinke>''s Falls, N. F. 



Productella costatula, Hall. 



Figs. 18. 19, 20. Three views of a pedicle-valve. 



Chemung group. Cliemimg county, iV. i'. 

 Fig. 35. The interior of a brachial valve. Above the tignre is an enlai'genient of the cai-dinal pi-oces.s. 



Chemung gi-oup. Cattaraugus county, JV. Y. 



Productella dumosa, Hall. 



Fig. 21. The exterior of a pedicle-valve, showing the i-ounded costa- with nnmerous spine-bases. 

 Hamilton group. CanandaigvM lake, N. Y. 



Productella lachrymosa, Coiuad, var. lima, Comad. 



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 Botdi, Hall. 



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



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 mncular 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 i;ardinal 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. Meadville, Permsylvania. 



Productella hystricula. Hall. 



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

 Fig. 30. The exterior of the pedicle-valve ; showing the tine, 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. 



