PLATE XI. 



CONCHIDIUM OBSOLETUM, Hall. 



Page 366. 



Figs. 1, 2. Dorsal and ventral views of an internal cast; showing the few low 

 and broad plications, the length of the median septum of the pedicle- valve, 

 the septal plates and muscular impressions of the brachial valve. 

 Niagara dolomites . Genoa, Ohio . 



CONCHIDIUM CRASSIPLICA, Hall. 



Page 367. 

 Figs. 3, 4. Dorsal and profile views; showing the ovate form of the shell, the 

 subequally convex valves, short and depressed beak of the pedicle-valve 

 and the coarse duphcate plication of the surface . 

 Niagara group . Probably from the vicinity of Louisville, Kentucky, 



CoNCHiDiuM Greenii, Hall. 



Page 367. 



Figs. 5, 6, 7. Ventral, cardinal and profile views of a specimen somewhat 

 restored about the margin; showing the short, ventricose valves and the 

 fine duplicate plication . . 

 Niagara dolomites . Near Milwaukee, Wisconsin . 



COKCHIDIUM SCOPABIUM, Hall. 



Page 366. 



Figs. 8, 9. Ventral and dorsal views of a specimen retaining much of the 

 shell and preserving a very distinct and rather fine radial plication. 

 Guelph dolomites. Durham, Ontario . 



CoNCHiDicM Geoegi^, Hall. 



Page 367. 



Figs. 10, 11 . Cardinal and dorsal views of the brachial valve, characterized by 

 its strong median fold . 

 Clinton group . Trenton, Georgia. 



Pentamkkus oblongus, var. Maquokkta, Hall. 

 Page 368. 



Figs. 12, 13. Dorsal and profile views of an internal cast; showing the ovoid 



and regularly convex valves. 

 Fig. 14. Cardinal view of another individual; showing the position and extent 

 of the internal plates . 

 Niagara dolomites. Near Dubuque, Iowa* 



396 



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