PLATE XXXVI. 
(Figures 1-30 by R. P. Whitfield.) 
Legend (except figure BO) : 
1). Deltiilial plates 
A. Dellhvriiim. 
t. 'J’eeth. 
d. Dental lamellae, 
y. Rostral cavity, 
s. Median septum 
Genus SPIRIFEE, Sowerby. 
Page 1. 
Spirieer crispus, Hisinger. 
j. Cardinal process. 
1). Dental sockets. 
c. Socket-walls. 
a. Adductor scars. 
d. Diductor scars. 
V. Vascular sinuses, 
Fig. 1. The exterior of a normal adult. X 2. 
Fig. 2. An enlargement of the umbonal region; showing the undefined cardinal area and incipient del- 
tidial plates. 
Niagara group. Rochester, N. F. 
Fig. 3. The interior of a pedicle-valve ; showing a more sharply defined area, and strong dental lamellae. 
X 3. 
Fig. 4. 1 'he interior of a brachial valve ; showing area and articulating apparatus. X 3. 
Niagara group. Waldron, Indiana. 
Fig. 5. An enlargement of a jwrtion of the interior of the brachial valve; showing the articulating 
apparatus and cardinal process. 
Fig. 6. An enlargement of the external surface; showing the closely crowded lainellse bearing bases of 
minute spinules. 
Niagara group. Rochester, N. F. 
Spirieer bicostatus, Hall. 
Fig. 7. The exterior of a normal specimen ; showing the lamellose sui-face. 
Niagara group. Vernon Center, IV. F. 
Spirieer tenuisiriatus, Hall. 
Fig. 8. View of the original specimen ; showing the radially striated plications. 
Lowei' Helderberg gi-oup. Decatur county, Tennessee. 
Spirieer crispatus, s}). nov. 
Figs. 9, 10. Views of a coarsely plicate, highly lamellose shell, probably representing an undescribed species. 
Niagai-a group. Maryland. 
Spirieer Vanuxemi, Hall. 
Pig. 11. The exterior of a normal individual; showing the elevation of the umbo of the pedicle-valve, the 
undefined cardinal area and the lamellose surface. X 2. 
Lower Helderberg group. Litchfield, N. Y. 
Spirieer cyclopterus, Hall. 
Fig. 12. The exterior of an average specimen. 
Fig. 13. The interior of a portion of a pedicle-valve ; showing teeth and muscular impression. X 2. 
Lower Helderberg grou}). Schoharie, N. F. 
