PLATE XXXVI. 



(Figures 1-30 by K. P. Whitfield.) 

 Legend (except figure 30) : 



1). Deltidial plates. j. Cardinal process. 



A- Delthyrium. b. Dental sockets. 



t. Teeth. c. Socket-walls, 



d. Dental lamellae. a. Adductor scars. 



y. Rostral cavity. d. Diductor scars, 



s. Median septum. v. Vascular sinuses. 



Genus SPIRIFER, Sowerby. 



Page 1. 



Spirifer CRISPU8, Hisiuger. 

 Fig-. 1. The exterior of a normal adult. X 3. 



Fig. 2. An enlargement of the nmbonal region ; showing the undefined cai-dinal area and incipient del- 

 tidial plates. 



Niagara group. Bochester, N. Y. 

 Fig. 3. The intenor of a pedicle-valve ; showing a more sharply defined area, and strong dental lamellse. 



X 3. 

 Fig. 4. The interior of a brachial valve ; showing area and articulating apparatus. X 3. 



Niagara group. JValdron, Indiana. 

 Fig. 5. An enlargement of a portion of the interior of the brachial valve; showing the articulating 



apparatus and cardinal process. 

 Fig. 6. All enlargement of the external surface ; showing the closely crowded laniellie bearing bases of 

 minute spinules. 



Niagara group. Bochester, N. Y. 



Spirifer bicostatus, Hall. 



Fig. 7. The exterior of a normal specimen ; showing the lamellose sui-face. 

 Niagara group. Vernon Center, N. Y. 



Spirifer tenuistriatus, Hall. 



Fig. 8. View of the original specimen ; showing the radially striated plications. 

 Lower Hel<ierberg group. Decatur county, Tennessee, 



Spirifer crispatus, sp. nov. 



Figs. 9, 10. Views of a coarsely plicate, highly lamellose shell, probably representing an undescribed species. 

 Niagara group. Maryland. 



Spirifer Vanuxemi, Hall. 



Fig. II. 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. T. 



Spikifer CYCLOPTERUS, Hall. 



Fig. 12. The exterior of an average specimen. 



Fig. 13. The intei-ior of a portion of a pedicle-valve ; showing teeth and muscular impression. X 2. 

 Lower Helderberg group. Sclwharie, N. Y. 



