PLATE XXXIV. 
(Figures 1-33 by R. P. Whitfield.) 
Legend: 
A. Cardinal area (outer division). 
j- 
Cardinal process. 
A'. Cardinal area (inner division). 
b. 
Dental sockets. 
A. Delthyrium. 
c. 
Socket-walls. 
s'. Delthyrial callosity. 
s. 
Median septum. 
t. Teeth 
a. 
Adductor scars. 
d. Dental lamellae. 
r. 
Diductor scars. 
Genus SPIRIFER, Sowerby. 
Page 1, 
Spirieer macrus, Hall. 
Fig. 1. The exterior of a pedicle-valve ; showing the lamellose character of the surface. 
Corniferous limestone. Western New York. 
Fig. 2. A cardinal view of an internal cast of the pedicle-valve. 
Fig. 3. An internal cast of the pedicle-valve ; showing the size of the muscular impression. 
Schoharie grit. Schoharie, N. T. 
Spirieer varicosus, Hall. 
Fig. 4. A brachial valve ; showing the character of the external surface. 
Fig. 5. A cardinal view; showing the height of the cardinal area and the width of the delthyrium. 
Fig. 6. The interior of a brachial valve ; showing the articulating apparatus. X 2. 
Fig. 7. The interior of a portion of the pedicle-valve with a highly developed delthyrial callosity. 
Fig. 8. An enlarged view of another specimen showing the same structure. 
Upper Helderberg group. Wiliiainsville and western New York. 
Spirieer oonsobrinus, (VOrhigiw (= Spirieer zic-zac, Hall). 
See Plate 35. 
Fig. 9. A normal adult; showing the lamellose exterior, and the sulcus on the median fold. 
Hamilton group. Western New York. 
Spirieer arctisegmentus, Hall. 
Fig. 10. A pedicle-valve, viewed from the ajiex. 
Fig. 11. A cardinal view of the same specimen ; showing the height of the area, its outer and inner divi¬ 
sions, and the form of the delthyrium. 
Fig. 12. An enlargement of the lamellose external surface. 
Hamilton group. Clarke county, Indiana. 
Spirieer mucronatus, Conrad. 
Fig. 13. A specimen of the usual foi-m and proportions in the soft shales ; showing the lamellose exterior. 
Fig. 14. A shorter and more rotund specimen. 
Hamilton group. Canandaigua Lake, N. Y. 
Fig. 15. A small pedicle-valve with highly extended cardinal extremities. 
Marcellus shales. Near Alden, N. Y. 
Fig. 16. A specimen with long, nan-ow, acuminate cardinal extremities. This is a somewhat unusual form. 
Hamilton group. Darien Center, N. Y. 
Fig. 17. The interior of a brachial valve ; showing the articulating apparatus and muscular area. 
Fig. 18. The interior of a jiedicle-valve ; showing the teeth and muscular area. 
Fig. 19. An enlargement of a portion of the brachial valve ; showing the detailed structure of the dental 
sockets, cardinal process and adductor muscular scars. 
Fig. 20. A similar enlargement of the corresponding parts of the pedicle-valve, the muscular impressions 
being much broader than in the preceding specimen. 
