PLATE XVI— Continned. 



Chonetes coronata, Conrad. 

 Fig. 10. A view of the V)iachial valve ; showing' the cariiinal area ami delliiliuin. 

 Figr- 11- A pedicle- valve with unusually strong concentnc growth-lines. 



Hamilton group. Daiien, N. Y. 

 Fig. 24. The interior of a brachial valve ; showing the cardinal process, muscular scai-s and brachial 

 ridges. 



Hamilton group. ForAr, N. Y. 

 Fig. 26. The interior of another brachial valve ; showing more distinctly the quadripartite character of the 



cardinal process. 

 Fig. 33! The interior of a pedicle-valve ; showing the cardinal area, teeth and muscular seal's. 

 Hamilton group. Western New York. 



Genus STROPHALOSIA, King. 



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

 Page 314. 



Strophalosia muricata, Hall. 



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



shoi't spines on the surface. 

 Fig. 16. Two views of a pedicle- valve ; showing the cicatnx of attachment. 

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



brachial ridges and median septum. 

 Fig. 38. An internal cast of the jiedicle-valve ; showing the muscular impressions. 



Fig. 42. An enlargement of the muscular scai-s restored from several intei-nal casts of the jiedicle-valve. 

 Chemung group. Meadville, Pennsylvania. 



Genus CHONOSTROPHIA, gen. nov. 



^(Seo Plate XVb.) 

 Page 310. 



Chonostrophia complanata, Hall. 



Fig. 13. The interior of the pedicle-valve from a giitta-per<ha impres.^ion ; showing the reversed convexity 

 of the shell, the tlabellate muscular area, conspii;uous median septum, and the cardinal spines. 

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

 Oriskany sandstone. Albany county, N. Y. 



Genus CHONETES, Fischer de Waldheim. 



Page 303. 



Chonetes HEMi.spH.ffiRicA, 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 peilic'le-valve, from which the radiating striic 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 

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

 Corniferous limestone. Near Willinmsmlle, N. Y. 



Genus CHONOPECTUS, gen. nov. 



(See Plate XVb.) 

 Pago 312. 



Chonopectu.s Fischeri, Norwood and Pratten. 

 Fig. 17. The exterior of a pediiMe-valve ; showing the concentrically reticulale surface. 

 Fig. 81. An enlargement of the surface ; showing the double series of conceutrio wrinkles crossing the fine 

 radiating striie. 



Yellow sandstones. Burlington, Iowa. 



