PLATE LXIV. 



(Kigureii 1-13 liy K. 1'. WiiiTFiKLl) ; 14-16 copies.) 



Genus CONCHIDIUM. Linn6. 



I'age-ai. 



CoNCHiDiuM Nysius, Hilll lllld Wliitfiold.* 



See foot-note on page 'iSi. 



FigB. 1, 2. Dorsal and profile views of a small, coarsely plicated shell. 

 RgB. 7, 8. Doreal and profile views of a large individual. 



Niagara group. Near LtmisvUle, Kentucky. ^ 



CoxcHiDiUM TENUicosTA, Hall aiul Wliitfield. 



Vign. 3, 4. Dorsal and cai-iiinal views vf an adult specimen, showing' the outline, contour and fine plication 



of the surfat-e. 

 Fig. 5. Dorsal view of a young individual. 



Niagara group. Near Ix>ultmUe, Kentucky. 



CONCHIDIUM MULTICOSTATUM, Hall. 



Fig. 6. Doisal view of an internal cast ; showing the fine plication about the margins. 

 Niagara group. Waukesha, Wisconsin. 



CONCHIDIUM LiTTONI, HuU. 



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. 



PigK. 11, 12, 13. Profile, dorsal and cardinal views of the oi-iginal specimen ; showing the contour and du- 

 plicate plication of the valves. 



Niagara group. Near Louisville, Kentucky. 



CONCHIDIUM Knighti, Sowei'by. 



Fig. 14. Longitudinal section of the valve-s ; .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 an<l the distal wall of that in the opposite valve. 



Amestry limestone. Near Leiiitwardine, >$hritpskire. 

 P!g». 15,16. Dorsal and profile views of an averafje typical example; showing the contour of the species, 

 consjiicuoufl and incurved umbo of the pedicle valve, and the complete plication of the surface. 

 Amestry limestone. Aymeslry, UnglaTid. 



(Figures 14-16 after Daviijion.) 



