PLATE 46. 
Legend: d. Spondylium. 1. Cruralium. _ 
s. Median septum (pedicle-valve). c. Crura. 
s'. Median septum (brachial valve). 
CONCHIDIUM, Liyne. 
Page 842. 
Concaipium wunéuIFormis, Ulrich. 
Figs. 1, 2. Dorsal and ventral views of the original specimen; showing the form 
of the shell, the character of its plication, its concentric varices and 
fine growth-lines. The drawings areslightly restored in the umbonal 
region of the pedicle-valve. 
Niagara group. Near Louisville, Kentucky. 
ConcHIDiIuM DECUSSATUM, Whiteaves. 
Fig. 3. Dorsal view of a small example; showing the form and exterior char- 
acters of the species. 
Niagara dolomites. Rapids of the Saskatchewan River, 
British America. 
Concuipiom Lirront, Hall. 
Figs. 4,5. Dorsal and profile views of an average specimen; showing the 
abundant plication of the surface and the characteristic breadth of 
the valves in the umbonal region. 
Niagara group. Hardin county, Tennessee. 
Concutpium Nystus, Hall and Whitfield. 
Figs. 6, 7. Dorsal and profile views of a large individual. 
Niagara group. Near Louisville, Kentucky. 
CoNCHIDIUM BILOCULARE, Linné. 
Fig. 8. A natural longitudinal section of conjoined valves; showing the 
relation of the spondylium and septal plates. 
Fig. 9. A profile of the same specimen; showing the long, concave and smooth 
cardinal slopes. 
Upper Silurian limestone. Island of Gotland. 
Concurpium Kyieutt, Sowerby. 
Fig. 10. Dorsal view 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. (DAVIDSON.) 
Aymestry limestone. Aymestry, England, 
250 
