PLATE XXXVI. 



(Figures 1-30 by K. 1'. WiHTi'IEi.D.) 



Legem! (except tij;iire 80) : 



I). Deltiilial plates. j. Cardinal process. 



A. Dellhyrinm. 1). Dental .sockets, 



t. Teeth. c. Socket-walls. 



(1. Dental lamellie. a. Adductor scai-s. 



y. Rostral cavity. d. Diductor scars. 



s. Median septum. v. Vascular sinuses. 



Genus SPIRIFER, Sowerby. 



Si'iKiFER CRisrus, Hisiiigcr. 



Fig. 1. The exterior of a normal adult. X 2. 



Fig-. 2. An enlargement of the umbonal region ; showing the undefined cardinal area and iticipiciit <lel- 

 tidial plates. 



Niagara group. Rochester, N. Y, 

 Fig. 3. The interior of a pedicle-valve ; showing a more sharply defined area, and strong dent.il lamella. 



X 3. 

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



Niagara group. JValdron, Indiana. 

 I'"ig. r>. An enlargement of a portion of the interior of the brachial valve; showing the ar-ticulating 



apparatus and cardinal proce.ss. 

 Fig. 6. An enlargement of the external surface ; showing the closely crow<leil lamelhe bearing bases of 

 minute spinules. 



Niagara group. Roclnster, N. Y. 



Sl'IKIFER BICOSTATU.f, HmII. 



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

 Niagara g-rou p. Vernon Center, N. Y. 



yriRIFKR TENUISTRIATUS, Hall. 



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

 Lower Helderberg group. Decatur county, Tennessee. 



Spirifer orispatus, sp. nov. 



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

 Niagara group. Maryland. 



SrruiFER Vanuxemi, H,-i11. 



Fig. 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. 



Spirifer cyclopterus, Hull. 



Fig. 12. The exterior of an average specimen. 



Fig. 13. The interior of a portion of a pedicle-valve ; sho-wing teeth and muscular impression. X 2. 

 Lower Helderbei-g group. Schoharie, N. Y. 



