PLATE XXXIV. 



(Figures 1-33 by R. P. Whitfiki.d.i 



Leg-end : A. Cimliiial area (outer division). j. Cjiidinal ))i'0(:ess. 



A'. Cardinal area (inner division). b. D(Mital so(!kels. 



A. Delthyrium. c. Sooket-walls. 



s'. Delthyrial calUxsity. .s. Median septum, 



t. Teeth a. Adductor scars, 



d. Dental lamellse. r. Diductor scars. 



Genus SPIRIFER, Soweuby. 



Pape 1. 



Spihifer maceus, H;ill. 



Fii^. 1. The exterior of a pedicle- valve ; showing- the lamellose character of the sni-face. 



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 muscidar impres.'iion. 



Schohai-ie grit. Schoharie, iV. T. 



Spirifer varicosus, Hall. 



Fig. 4. A brachial valve ; showing the character of the external surface. 



Fig. 5. A cardin.ll view ; showing the height of the cardinal area and the width of the delthyi-inin. 



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. 



Uppei' Helderbei-g group. Williaiiisiiille and western New York. 



Spirifer consobrinus, d'Orbigiiy (= Spirifer zic-zac, II.ill). 



See Plate 35. 

 Fig. fl. A normal adult ; showing the lamellose exterior, .ind the sulcus on the median fold. 

 Hamilton group. Western New York. 



Spirifer arctisegmentus, Htill. 



Fig. 10. A pedicle-valve, viewed fi-om the apex. 



Fig. 11. A cardinal view of the same sj^ecimen ; 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. 



Spirifer muceonatus, Connid. 



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-v.alve with highly extended cardinal extremities. 



Marcellus shales. Near Alden, N. Y. 

 Fig. 16. A specimen with long, narrow, acuminate cai'diual extremities. This is a somewhat unusual form. 



Hamilton group. Darien Centei; N. Y. 

 Fig. 17. The interior of a brachial valve ; showing the articulating apjiaratus and muscular area. 

 Fig. 18. The interior of a pedicle-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. 



