PLATE XXII. 
(Figures 1-7, 9-U, 17, 18, 22-24 by R. P. Whitfield; 8, 15, 16, 19-21 by P. B. Meek.) 
A. Cardinal area, iiedicle-valve. 
r. Diductor scars. 
t. Teeth. 
c^. Socket-walls. 
a. Median ridge. 
j. Cardinal x^rocess. 
Callosity in delthyrium. 
b. Dental sockets. 
Genus SPIRIFEK, Sowerby. 
Page 1. 
Spirieer Oweni, Hall. 
Fig. 1. Dorsal view of a normal adult. 
Fig. 2. A pi'otile of the same. 
Fig. 3. The interior of the cardinal portion of a brachial valve; showing the dental sockets and socket- 
walls. 
Fig. 4. A-portion of the interior of the pedicle-valve; showing the apical callosity, and the scar of the 
diductor muscles. 
Fig. 5. A corre.sponding portion of a smallei’ shell of this species. 
Fig. 6. The interior of the cardinal portion of two valves in aidiculation, the pedicle-valve lying beneath. 
Fig. 7. An enlargement of the surface from a worn specimen. 
Hamilton group. Clarke county, Indiana. 
Spirieer Parryanus, Hall. 
Fig. 8. The usual form of the shell; the cardinal area being foreshortened. 
Fig. 9. An enlargement of the surface characters. 
Limestones of the Hamilton gi-oup. Davenpm't, Iowa. 
Figs. 15, 16. Two views of an internal cast. This is the condition of the shell which has been known as 
S. capax. Hall. 
Fig. 17. An enlargement of surface strife, in a worn specimen. 
Sandstones of the Hamilton group. Mouth of Pine Creek, Iowa. 
Spirieer Marcyi, Hull. 
Fig. 10. A normal individual, from which the cai-dinal extremities have been broken. 
Fig. 11. A cai'dinal view of the same example. 
Fig. 12. The interior of a brachial valve; showing the articulating apparatus. 
Fig. 13. The interior of a fractured and incomplete portion of the jiedicle-valve. 
Fig. 14. An enlargement of the surface ; showing the elongate, lachrymiforrn pustules. 
Hamilton group. Genesee cotmty, N. Y. 
Spirieer Tullius, Hull. 
Fig. 18. The exterior of a pedicle-valve. 
Hamilton shales. Onondaga county, N. Y. 
Spirieer ligus (= Spirieer pennatus), Owen. 
Fig. 19. An adult individual; showing noianal chai-acters. 
Fig. 20. A smaller individual. 
Fig. 21. Cardinal views of articulated valves. 
Figs. 22-24. Enlargements of the surface, in different conditions of preservation. Figs. 22 and 24, X 5; 
tig. 23 a higher enlargement from a poi'tion of tig. 22, in which the fine radiating surface lines 
are lost. 
Hamilton group. New Buffalo and Independence, Iowa. 
