PLATE XXXV. 



Legend : 



Genus SPIRIFER, Sowerby. 



Page 1. 



Spikifer sulcatus, Hisinger. 



Pig. 1. An individual of normal proportions ; showing the lamellose exterior. 



Figs. 2, 3. Enlargements of the central portion of the cardinal area of two examples. The deltidial plates 



have not united in either specimen, but have attained a more advanced development in fig. 2 



than in fig. 3. 

 Fig. 4. Enlargement of the external lamellose surface ; showing the minute pustules on the radial stria- 



tions. 



Niagara group. LockpoH, N. Y. 



SpIRIFEK RARICO.STU8, Coimicl. 



Fig. 5. A brachial view of a specimen of ordinary size. 



Fig. 6. An enlargement of the surface of the same specimen ; showing the inequidistant lamellse. 

 Comiferous limestone. Central New York. 



SpIRIFER PERLAMELL08US, Hall. 



Fig. 7. A normal adult shell, retaining the deltidial covering and foramen. 



Fig. 8. A median lonfjitudinal section of conjoined valves ; showing the dental plates and median septum 



of the pedicle-valve and the crura of the brachial valve. 

 Fig. 9. An enlargement of the external surface ; showing the crowded and radially striated lamellse. 

 Fig. 10. An enlargement of the central portion of the cardinal area, bearing a perforated deltidial covering 



in which the plates are completely coalesced and extend to the beak of the brachial valve. 

 Fig. 11. A similar enlargement from another specimen, having a shorter deltidial covering. 

 Fig. 12. The interior of a pedicle-valve ; shoNving the imjierforate deltidial covering and the median 



septum. 

 Fig. 13. An enlargement of the central portion of a brachial valve ; showing the crura and the jteculiar 



bilobed form of the cardinal process lying at the base of the socket-walls. 

 Lower Helderberg group. The Helderbergs, N. Y. 



Spirifer rarioostus, Conrad. 



Fig. 14. An enlargement of the central portion of the cardinal area ; showing its transverse striation and 

 the incipient deltidial plates. 



Corniferous limestone. Albany county, N. Y. 

 Fig. 15. An oblique view of the pedicle-valve ; showing the median septum. 



Comiferous limestone. Western New York. 

 Fig. 16. The interior of a pedicle-valve of a small imlividual ; showing the teeth and low septum. 

 Pig. 17. An interaal cast of a pedicle-valve ; showing the filling of the rostral cavity, the position of the 

 median septum and the impression of the muscular scare. 

 Schoharie grit. Albany county, N. Y. 



