PLATE XYIIa. 
(Figures 1-5, 8, 9,11, 12, 14, 21, 25, 26 by E. Emmons ; 6, 7,10,13,15-20, 22-24 by G. B. Simpson.) 
Legend. A. Cardinal area (pedicle-valve). 
D. Deltidium (pedicle-valve). 
C. Deltidium (brachial valve), 
j. Cardinal process, 
t. Teeth. 
x. Scar of attachment, 
z. Posterior ridge limiting internal cavity, 
a. Anterior adductor scars. 
a,'. Posterior adductor scars, 
r. Diductor scars. 
Genus STROPHALOSIA, King. 
(See Plates XVb and XVII.) 
Page 314. 
Strophalosia Rockfordensis, sp. nov. 
Fig. 1. A view of an imperfect specimen which retains the cardinal area and deltidium of each valve. X 2. 
Fig. 2. Cardinal view of the same specimen ; showing the scar of attachment. X 2. 
Upper Devonian. Rockford, Iowa. 
Strophalosia cymbula, sp. nov. 
Figs. 3, 4. Opposite sides of the same specimen ; showing the cardinal areas, deltidiaand scar of attachment. 
Keokuk group. Lebanon, Kentucky. 
Figs. 8, 9. Opposite sides of a larger individual, which is somewhat crushed at the apex of the brachial 
valve. 
Keokuk group. South of Louisville, Kentucky. 
Strophalosia Keokuk, Beecher. 
Fig. 5. A small individual; showing the great length of the spines. 
Fig. 6. An attached specimen ; showing deltidia, cardinal areas and adherent spines. X 2. 
Fig. 7. The cardinal portion of the same specimen enlarged to show the prolongation of the deltidium into 
a tube or sheath for the pedicle. X 4. 
Keokuk group. Crawfordsville, Indiana. 
Genus PRODUCTELLA, Hall. 
(See Plate XVII.) 
Page 328. 
Productella, sp. (?) 
Fig. 10. Cardinal view of an undetermined species, which retains the cardinal areas and deltidia of both 
valves and the marginal spines of the pedicle-valve. X 2. 
Chemung group. Greenwood, IV. Y. 
Productella pyxidata, Hall. 
(See Plate XVII, fig. 34.) 
Fig. 14. The cardinal portion of the pedicle-valve; showing the area and teeth. X 2. 
Choteau limestone. Pike county, Missouri. 
Genus PRODUCTUS, Sowerby. 
(See Plates XVI11 and XIX.) 
Page 321. 
Productus (Marginifera ? ?) DissiMiLis. Hall (= Productella Hallana , Walcott). 
Fig. 11. The interior of a pedicle- valve ; showing the sharp, papillose ridges or platforms diverging from 
the umbo. X 2. 
Fig. 12. The interior of a brachial valve which shows corresponding pitted ridges diverging from the bases 
of the cardinal process. This specimen also shows the remarkably extended brachial areas. 
Upper Devonian. Lime Creek, Iowa. 
