PLATE XVI— Continued. 



Chonetes coronata, Conrad. 



Fig. 10. A view of the bi'achial valve ; showing the cardinal ai-ea and deltidinm. 

 Fig. 11. A pedicle- valve with unusually strong concentric growth-lines. 



Hamilton gi-oup. Danen, N. T. 

 Pig. 24. The interior of a brachial valve ; showing the cai-dinal process, muscular scai-s and brachial 

 ridges. 



Hamilton group. YarJc, N. Y. 

 Pig. 26. The intei-ior of another brachial valve ; showing more distinctly the quadiipai-tite character of the 



cardinal pi-ocess. 

 Fig. 33. The interior of a pedicle-valve ; showing the cardinal area, teeth and muscular scars. 



Hamilton group. Western New York. 



Gends STROPHALOSIA, King. 



(See Plate-s XVb, XVII, XVIIa.) 

 Page 311. 



Strophalosia muricata, Hall. 



Fig. 12. The exterioi- of the pedicle-valve, from a gutta-percha impi-ession of a natural mould ; showing the 



short sx^ines on the surface. 

 Fig. 16. Two views of a pedicle- valve ; shovidng the cicatrix of attachment. 

 Fig. 30. The interior of a brachial valve, from a gutta-xiercha impression ; showing the cardinal process, 



brachial ridges and median septum. 

 Fig. 38. A.n internal cast of the pedicle-valve ; showing the muscular impressions. 



Fig. 42. An enlai-gement of the musculai' seal's restored from several interaal casts of the pedicle-valve. 

 Chemung group. Meadville, Peniisylvania. 



Genus CHONOSTROPHIA, gen. nov. 



^(See Plate XVb.) 

 Page 310. 



Chonostrophia complanata, Hall. 



Fig. 13. The interior of the pedicle-valve from a gutta-percha impi-ession ; showing the reversed convexity 



of the shell, the flabellate muscular area, conspicuous median septum, and the cardinal spines. 

 Fig. 29. Another interior of a similar valve in which the cardinal spines are apparently absent. 

 Oriskany sandstone. Albany cmmty, N. Y. 



Genus CHONETES, Fischer de Waldheim. 



Page 303. 



Chonetes hemisphjlrica, Hall. 



Fig. 14. A view of the pedicle-valve; showing its great convexity. 

 Schoharie grit. Albany county, N. Y. 



Chonetes arcuata, Hall. 



Fig. 15. Profile of a pedicle-valve, from which the radiating striaj have been accidentally omitted in litho- 

 graphing. 



Figs. 35, 36. Two views of an internal cast of the pedicle-valve ; showing the muscular impressions and the 

 crenulation of the cardinal area, caused by the casts of the spine-tubes. 

 Corniferous limestone. Near WilUamsville, N. Y. 



Genus CHONOPECTUS, gen. nov. 



(See Plate XVjb.) 

 Page 312. 

 Chonopectus Fischeri, Norwood and Pratten. 

 Pig. 17. The exterior of a pedicle-valve ; showing the concentrically reticulate surface. 

 Fig. 31. An enlargement of the surface ; showing the double series of concentric wrinkles ci-ossing the fine 

 radiating striae. 



Yellow sandstones. Burlington, Iowa. 



