PLATE XVIIa. 



(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. SiMl'SON.) 

 Leg-end. A. Canlinal aiv.i (iicdicle-valvp). x. Scar of attachment. 



D. Deltiiiium (pedicle-valve). z. Posterior riiifre limitinjf internal cavity. 



C. Deltiiiium (brachial valve). a. Anterior aildnctor scars, 



j. Cardinal process. a'. Postei-ior adductor scars. 



t. Teeth. r. Diductor si^i-s. 



Genus STROPIIALOSIA, King. 



(See Plates XVii and XVll.) 

 Page 314. 



Strophalosia Rockfordensis, sp. IIOV. 



Fig. 1. A view of an imperfect specimen which retain.'; the cardinal area and deltidiiim of each valve. X 2. 

 Fig. 2. Cardinal view of the same specimen ; .showing the acar of attachment. X 2. 

 Upper Devonian. Rockford, Icnoa. 



Strophalosia crMBULA, sp. nov. 



Figs 3, 4. Opposite sides of the same specimen ; showing the cardinal aieas,deUidia and scar of attachment. 



Keokuk group. Lebano7i, Kentitcky. 

 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 enlai'ged to show the prolongation of the deltidiuni into 

 a tube or sheath for the pedicle. X 4. 



Keokuk group. Orawfordsmlle, Indiana. 



Genus PRODUCTELLA, Hall. 



(See Plate XVIL) 

 Page 338. 



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. Q-reenviood, N. Y. 



Productella pyxidata, Hall. 



(See Plate XVII, lig. 34.) 

 Fig. 14. The cardinal portion of the pedicle-valve ; showing the area and teeth. X 2. 

 Choteau limestone. Pike county, yiissouri. 



Genus PRODUCTUS, Sowerby. 



(See Plates XVI U and XIX.) 

 P.-ige 321. 



Productus (Maeginifera ? ?) DissiMiLis. Hull (= Piodmlella Hallana, Wulcott). 



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 I'idges diverging fi-om the bases 



of the cardinal process. This specimen also shows the remarkably extended brachial areas. 



X 2. 



Upper Devonian. Lime Creek, Iowa. 



