PLATE XVIII. 
(Figures 1-5,14-17,19 by R. P. Whitfield ; 6-13,18 by F. B. Meek.) 
Legend, j. Cardinal process. a. Anterior adductors. 
s. Septum, 
v. Brachial ridges. 
a'. Posterior adductors, 
r. Diductors. 
Genus PRODUCTUS, Sowerby. 
(See Plates XVIIa, and XIX.) 
Page 321. 
Productus Newberryi, Hall. 
Fig. 1. The exterior of a pedicle-valve; showing the numerous spine-bases and retaining the spines at the 
cardinal extremities. 
Waverly sandstone. Medina, Ohio. 
Fig. 2. An internal cast of the united valves ; showing the muscular impressions of the brachial valve and 
the brachial ridges. 
Fig. 3. An internal cast of a pedicle-valve ; showing the adductor and diductor impressions. 
Waverly sandstone. Newark, Ohio. 
Productus, sp. ? compare Prattenanus, Norwood. 
Fig. 4. An undetermined pedicle-valve belonging to the group of the Striati. 
Waverly sandstone. Newark, Ohio. 
Productus, ? sp. ? 
Fig. 5. Profile of a pedicle-valve, with spiniferous costae. 
Chemung group. Cattaraugus county, N. Y. 
Productus Flemingi, Sowerby, var. Burlingtonensis, Hall. 
Figs. 6, 7, 8. Three views of a pedicle-valve. 
Burlington limestone. Burlington, Iowa. 
Productus mesialis, Hall. 
Figs. 9, 10. Tw 
i views of a pedicle-valve. 
Keokuk group. Nauvoo, Illinois. 
Productus semireticulatus, Martin. 
Fig. 11. A cast of the exterior of a large brachial valve ; showing the surface characters. 
Fig. 12. A cardinal view of the pedicle-valve. 
Fig. 13. A view of a specimen having the valves united and retaining some of the cardinal spines on the 
pedicle-valve. 
Keokuk group. Warsaw, Illinois. 
Productus alternatus, Norwood and Pratten. 
Fig. 14. A pedicle-valve with the peculiar surface markings, which are due to the exfoliation of the spine- 
Keokuk group. Illinois. 
