PLATE XLVI— Continued. 

 Fig. 18. The exterior of a pedicle- valve ; showing' the noi'mal marginal outline of the species. 

 Fig. 19. The exterior of a large brachial valve with few and distant lamellie and unusually extended 

 hinge-line. The tirst of these lamella! bears a serrated margin, while the rest are regular. 

 The anterior and lateral margins of the valve are concealed by the great ex)iansion of the 

 submarginal lamella. 



Keokuk group. Crawfm-dmntle, Indiana. 

 Fig. 20. The central cardinal portion of an internal cast of conjoined valves, enlarged ; showing the posi- 

 tion of the teeth, dental plates and hiiige-j)late, the filling of the pedicle-cavity and viscei'al 

 foramen, the latter being tj-aversed for its entire length by a median gi-oove, representing a 

 faint median ri<lge upon the brachial valve, extending from the apex across the muscular 

 area. X 3. 



Wavei'ly group. iSeiotoville, Ohio. 



Athyris incrassata, Hali. 



Fig. 21. The exterior of a somewhat weathered pedicle-valve. 

 Burlington limestone. Burlington, Iowa. 



Genus SPIRIFER, Sowerby. 



Page 1. 

 Fig. 22. This figure is an enlarged representation of an internal cast of a small pedicle-valve belonging to 

 a species of Spiiufer similar to S. pxeiidolineatii^. Hall. This fossil occurs in the soft shales of 

 the Waverly group, and its generic characters are usually ol)scured. Its relation to Spirifer 

 is indicated by the long, thin denial lamellae, low median se])tum, and fine surface spines which 

 are plainly double-barrelled at the base. Additional specimens obtained since this plate was 

 engraved show that these spines bear series of short lateral branches. 

 Waverly group. Richfield, Ohio. 



Genus ATHYRIS, McCor. 



Page 83. 



Subgenus CLIOTHYRIS, King. 

 Cliothyrls Roysii, Leveille. 



Fig. 23. Dorsal view of conjoined valves ; showing the concentric rows of flat spines. X 2. 



Keokuk group. Keokuk, Iowa. 

 Fig, 24. An enlargement of a portion of the surface. 



Chester limestone. .laekson county, Kentucky. 



Cliotiiyris hirsuta, Hall. 



Fig. 25. Dorsal view of an average specimen denuded of its spines. X 2. 



Fig. 26. A larger specimen with portions of the i-ows of flat spines adhering. X 2. 



Fig. 27. View of the hinge-plate ; showing the crescentiform wall made by the crural lobes, and the thick 



central lobe of the plate. X 5. 

 Fig. 2S. The same specimen viewed from in fi-ont ; showing the elevation of the hinge-plate, the crural 



bases and the minute visceral foramen which is usually closed in its upward extension. X 5. 

 St. Louis limestone. Bloomington, Indiatia. 



