PLATE LXIV. 



(Figures 1-13 by K. 1'. Wlini'iELD ; 14-Iii cciiiies.) 



Genus CONCHIDIUM. Linn6. 



I>age231. 



CONCHIDIUM NySIUS, IIllll ;lll(l Wllitflcld.* 



8ee foot-note on page 235. 



Fig's. 1, 2. Dorsal and profile views of a small, coarsely plicated shell. 

 Figs. 7, 8. Dorsal and profile views of a large individual. 



Niagara grotip. Near Lauwmlle, Kenhwky. 



CoxcniDiuM TENUicosTA, Hall and Whitfield. 



Figs. 3, i. Dorsal and cardinal views of an adult specimen, showing the outline, contour and tine plication 



of the surface. 

 Fig. 5. Dorsal view of a young individual. 



Niagara group. Near Louisville, Kentucky. 



CONCHrDIUM MULTICOSTATUM, ILlll. 

 Fig. 6. Doisal 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 unibonal region. 

 Niagara group. Hardin cou7i,ty, Tennessee. 



CoNCHiDiUM Knappi, Hall and Whitlield. 



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 Ltmisville, Kentucky. 



CoNCHiDiuM Knighti, Sowciby. 



Fig. 14. Longituiiinal section of the valves ; showing the development of the spondylia and median septa. 

 The specimen is so liroken as to exhibit the proximal wall of the spondyliura of the pedicle- 

 valve and the distal wall of that in the opposite valve. 



Amestry limestone. Near Leintwardine, Shropshire. 

 Fis's. 15, Iti. 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. AymeMry, England. 



(Figures 14-16 after D.wil.son.) 



