PLATE XXIV. 



(Ftgare* 1-47 by B. P. Whitfield.) 



Lag«nd: A- DeUhyrium. l>. Dental Bocketa. 



D. Deltidiiim. c'. Socket-walls. 



Dg. Deltidial grooves. a. Anterior adductors. 



t. Teeth. a'. Posterior adductors. 



s'. Apical callosity. r. Diductoi-s. 

 j. Cardinal process. 



Genus SPIRIFER, Sowerby. 



rage 1. 



Spirifer AUDACULU8, Coiuad. 



A small individual of normal proportiuns. 

 3. A brachial valve of an average example. 

 3. The j)edicle-valve of a i-otund specimen. 



5. Doi-sal and profile views of an individual with short hinge and fewer plications. 

 . Front view of an average adult. 



. The interior of the brachial valve ; showing the articulating apparatus and muscular scars. 

 . A cardinal portion of a larger brachial valve ; showing the same structures more distinctly. 

 . The interior of a pedicle-valve ; showing the formation of the apical callosity, and the character of 

 the muscular area. 

 Fig. 10. The central portion of the cardinal area of the pedicle- valve, i-etaining the remnants of the del- 



tidial covering. X 2. 

 Fig. 11. A similar view of another example j showing the high development of the delthyinal callosity. 

 Fig. 12. A part of the brachial valve ; showing the cardinal process, articulating apparatus and the char- 

 acter of the adductor scars. X 2. 

 Fig. 13. An enlargement of the external surface ; showing the grooves on the summits of the plications. 

 Hamilton shales. Western New York. 



Spirifer angustus, Hall. 



Figs. 14, 15. Dorsal and ventral views of the exterior of a rather large individual. 



Fig. 16. A cardinal view of the same specimen. 



Fig. 17. An enlargement of the external surface j showing the flattened plications and incipient grooves. 



Spirifer audaculus, var. macronotus, Hall. 



Fig. 18. A cardinal view of a large individual which retains the deltidial cuvei'ing in a broken condition. 



Fig. 19. A cardinal view of a shallower, more extended individual. 



Fig. 20. A profile view of the same. 



Fig. 21. A view of the intei-ior of the pedicle-valve, looking into the umbonal cavity ; showing the callosity 

 and dental plates. 



Fig. 22. Central jwrtion of the cardinal area; Rhowing the highly developed dellhyrial callosity. X 2. 



Fig. 23. A similar view of another specimen in which the deltidial covenng is retained in a bi-oken con- 

 dition. 



Fig. 24. The interior of a part of the pedicle-valve ; showing the divisions of the muscular area, and the 

 thickened dental ridges. 



Fig. 2.'). The interior of a similar specimen, the apex being removed to show more clearly the details of 

 the muscular impression. 



Figs. 26, 27. Enlargements of the external surface ; showing characters which are often seen on the same 

 shell. 



Hamilton shales. Western New York. 



