PLATE LVIII. 
(Figures l-IO, 16-19, 21, 25, 36, 10 by G B. Simpson; 11, 12,14, 35 by E. Emmons; 13, 20-23,26-33 by F. B. Meek.) 
Genus KHYNCHOPORA, King 
Page 210. 
Rhynchopoka pustulosa, White. 
Figs. 1-4. Doi'sal, ventral, front and profile views of an aveiage example. 
Burlington limestone. Burlingtmi, Iowa. 
Genus WILSONIA, (Quenstedt) Kaysek. 
Page 195 
WiLSONIA SaEFORDI, Hilll. 
Figs. 5-7, 10. Dorsal, ventral, frontal and profile views of a normal adult individual. 
Figs. 8, 9. Front and profile views of another specimen, with broader median fold and greater anterior 
gibbosity. 
11. The interior of a pedicle-valve ; showing the teeth and muscular impressions. X 2. 
12. Cardinal view of an internal cast of conjoined valves ; showing the muscular impressions and the 
cavities left by the dental plates and median septum. X 2. 
Niagai'a group. Perry county, Tennessee. 
WiLSONIA VENTKICOSA, Hull. 
13. Profile view of an average specimen ; showing the extreme gibbosity of the valves. 
14. The interior of a thickened pedicle-valve ; showing the scars of the pedicle and diductor muscles. 
Lower Helderberg group (Upper Pentamerus limestone). /Schoharie county, N. Y. 
Genus UjS’CINULUS, Bayle. 
Page 195. 
Uncinulus ABRUPTUS, Hull. 
15. The interior of the umbonal portion of the pedicle-valve ; showing the marginal teeth with dental 
plates lying close against the shell-walls. X 2. 
16. Cardinal view of the articulating apparatus of the brachial valve of a young shell; showing the 
triangular, divided cardinal process and the elevation of the crura. X 3. 
17. 18. Two views of the coiTesponding parts in an adult shell in which the lobes of the cardinal pro¬ 
cess and the lateral portions of the hinge-plate are considerably thickened. X 2. 
19. The interior of a pedicle-valve ; showing the faintly defined muscular scar. 
20, 21. Dorsal and front views of conjoined valves of a typical specimen. 
Lower Helderberg group (Shaly limestone). Albany and Schoharie counties, N. Y. 
Uncinulus mutabilis, Hall. 
Figs. 22, 23. Profile and front views of a mature shell; showing its subspherical shape. 
Figs. 24, 25. Two views of the interior umbonal region of the brachial valve; showing the thickened 
median septum, curved and elevated crura and bilobed cardinal process. X 14- 
Lower Helderberg group (Shaly limestone). Albany and Schohane counties, JY. Y. 
Uncinulus nobilis, Hall. 
Fig. 26. Front marginal view of an adult shell. 
Lower Helderberg group (Upper Pentamerus limestone.) Albany and Schoharie 
counties, JY. Y. 
Uncinulus pyramiuatus, Hall. 
Figs. 27, 28. Profile and front views of an average specimen. 
Lower Helderberg group (Shaly limestone). Albany county, N. Y. 
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