PLATE LXIV. 
(Figures 1-13 by K. P. Whitfield ; 14-16 copies.) 
Genus CONCHIDIUM, Linne. 
Page 231. 
CoNCHiDiuM Nysius, Hall and Whitfield.* 
See foot-note on page 235. 
Figs. 1, 2. Dorsal and profile views of a small, coarsely plicated shell. 
Figs. 7, 8. Dorsal and profile views of a larg-e individual. 
Niagara group. Near Louisville, Kentucky. 
CoNCiiiDiuM TENUicoSTA, Hall aiid Whitfield. 
Figs. 3, 4. Dorsal and cardinal views of an adult specimen, showing the outline, contour and fine plication 
of the surface. 
Fig. 5. Dorsal view of a young individual. 
Niagara grouii. Near Louisville, Kentiocky. 
CONCHlDIUM MULTICOSTATUM, Hilll. 
Fig. 6. Dorsal view of an internal cast; showing the fine plication about the margins. 
Niagara group. Waukesha, Wisconsin. 
CONCHIDIUM Littoni, Hall. 
Figs. 9, 10. Dorsal and profile views of an average specimen ; showing the abundant plication of the sur¬ 
face and the characteristic breadth of the valves in the umbonal region. 
Niagara group. Hardin county, Tennessee. 
CoNCHiDiuM Knappi, Hall and Whitfield. 
Figs. 11, 12, 13. Profile, dorsal and cardinal views of the original specimen ; showing the contour and du¬ 
plicate plication of the valves. 
Niagara group. Near Louisville, Kentucky. 
('’oNCHiDiuM Knighti, Sowerbj. 
Fig. 14. Longitudinal section of tlie valves ; showing the development of the spondylia and median septa. 
The specimen is so broken as to exhibit the proximal wall of the spondylium of the pedicle- 
valve and the distal wall of that in the opjiosite valve. 
Amestry limestone. Near Leintwardine, /Shropshire. 
Figs, 15, 16. Dorsal and profile views of an average typical example; showing the contour of the species, 
conspicuous and incurved umbo of the pedicle valve, and the complete plication of the surface. 
Amestry limestone. Aymestry, England. 
(Figures 14-16 after Davilson.) 
