PLATE XXII. 



(Flinra* 1-7. V-H. n, U. n-U bj B. P. Whitfibu); 8, IS, U, IB-Sl bj F. B. Hebk.) 



L(g«nd : A. Canlinal area, jiedicle-valve. r. Diductor scars, 



t. Teeth. c'. Socket- walls. 



8. Median ridg«. j. CariHnal process. 



8', s". Callosity in dellbyrium. b. Dental sockets. 



Genus SPIRIFEU, Sowerby. 



I>a«;e I. 



SriKiFEK Owen I, Hull. 

 Dorfial view of a normal adidt. 

 A profile of the same. 



The interior of the cardinal portion of a brachial valve j showing the dental sockets and socket- 

 walls. 

 Fig. 4. A portion of the interior of the jiedicle-valve ; showing the apical callosity, and the scar of the 



diductor muscles. 

 Fijf. 6. A corresponding portion of a smaller shell of this species. 



Fig. 6. The interior of the cardinal portion of two valves in articulation, the pedicle-valve lying beneath. 

 Fig. 7. An enlargement of the surface from a worn specimen. 

 Hamilton group- Clarke county, Indiana. 



SriBirEK Paukyanus, Hall. 



Fig. 8. The usual form of the shell ; the cardinal area being foreshortened. 

 Fig. 9. An enlargement of the surface charactei-s. 



Limestones of the Hamilton group. Davenport, 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 strise, in a woin sjiecimen. 



Sandstones of the Hamilton group. Mouth of Pine Creek, Iowa. 



Spiru'ek Makcyi, Hull. 



Fig. 10. A normal individual, from which the cardinal extremities have been broken. 

 Fig. 11. A cardinal view of the same example. 



Fig. 12. The interior of a brachial valve ; showing the articulating apparatus. 

 Fig. 13. The interior of a fractjired and incomplete portion of the pedicle-valve. 

 Fig. 14. An enlargement of the surface ; showing the elongate, lachrymiform pustules. 

 Hamilton group. Genesee county, N. T. 



Spikifek TULLIUS, Hull. 

 Fig. 18. The exterior of a pedicle-valve. 



Hamilton shales. Chumdaga county, iV. F. 



Spikifeb ligus (= Spiblfeb pennatus), Owen. 



Fig. 19. An adult individual ; showing normal characters. 



Fig. 20. A smaller indivi<lual. 



Fig. 21. Cardinal views of articulated valves. 



Figs. 22-24. Enlargements of the surface, in different conditions of preservation. Figs. 22 and 24, X ; 



fig. 23 a higher enlargement from a portion of fig. 22, in which the fine radiating surface lines 



are lost. 



Hamilton group. New Buffalo and iTidependence, Iowa. 



