PLATE XLVI—Continued. 
Kg’. 18. The exterior of a pedicle-valve ; showing the normal marginal outline of the species. 
Fig. 19. The exterior of a large brachial valve with few and distant lamellae and unusually extended 
hinge-line. The first of these lamellae bears a serrated margin, while the rest are regular. 
The anterior and lateral margins of the valve are concealed by the great exjiansion of the 
submarginal lamella. 
Keokuk group. Qraiofoi'dsville, 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 hinge-plate, the filling of the pedicle-cavity and viscei'al 
foramen, the latter being tj-avei'sed for its entire length by a median groove, representing a 
faint median i-idge upon the brachial valve, extending from the apex across the muscular 
area. X 3. 
Waverly group. Sciotoville, Ohio. 
AtHYRIS INCRASSATA, Hall. 
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 Spiripbk similar to S. pneudolineattbs. Hall. This fossil occurs in the soft shales of 
the Waverly group, and its generic characters are usually obscured. Its relation to Spirifee 
is indicated by the long, thin dental lamella, low median septum, 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, McCoy. 
Page 83. 
Subgenus CLIOTHYRIS, King. 
Cliothyris Roysii, Leveille. 
Fig^ 23. Dorsal view of conjoined valves ; showing the concentric rows of fiat spines. X 2. 
Keokuk group. Keokuk, Iowa. 
Fig. 24. An enlargement of a portion of the surface. 
Chester limestone. Jackson county, Kentucky. 
Cliothyris 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 rows 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. 28, 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, Indiana. 
