I'LATK XXXVI— Contlmiod. 



Gknus SPililFERINA, oORniGNY. 



I'ape 51. 



Spiriferina Kkntuckiensis, Slnmiard. 



Pi(f. 14. The extenor of a iieilicle- valve. 



Fig. 16. An oblique \'iew of the interic'r of the pedicle-valve ; showing' the median septum and muscular 



impressions. 

 Vig. 16. The cantinal view of an exfoliated shell ; showing the character of the ai-eaand deltidial plates. 

 Coal Measures. Illinois. 



Genus SPIKIFER, Sowerby. 



Page 1. 

 SpIRIFER FIMBRIATUS, Colirild. 

 See Plate 38. 

 Rg. 17. The internal cast of a pedicle-valve ; showing the composition of the muscular area. 



Schoharie grit. Schoharie, N. Y. 

 Figs. 18, 19. Dorsal and profile views of a normal example ; showing the lateral plications and the con- 

 centrically striated surface covered with the bases of spinules. 

 Upper Helderherg group. Western i\*eio York. 

 Fig. 20. An enlai-gement of the surface ; showing the bases of the spinules. 

 V\g. 21. A pedicle-valve which retains a poi-tion of the spinules. 



Hamilton group. Western New York. 

 Pig. 22. A cardinal view of an internal cast of conjoined valves ; showing the vascular sinuses. 

 Hamilton group. Hardy county, Virginia. 



Spirifer prjEmaturus, Hall. 



Pig. 23. The internal cast of a pedicle-valve, retaining a trace of a median septum. 



Chemung group. Allegany county, N. Y. 

 Fig. 24. The interaal cast of a pedicle-valve ; showing the impressions of the dental lamellie and a low 



median sex)tum. 

 Fig. [25. Another cast of the i>edicle- valve, which retains the muscular impression. 

 Chemung group. MeadvUle, Peimsyleania. 



Spirifek setigerus, Hall. 



Figs. 26, 27. Dorsal and profile views of a rotund, normal example; showing the incipient deltidial plates 

 and fimbriated lamellffi. 



Chester limestone. Chester, Illinois. 



Spirifer pseudolineatus, Hall. 



Fig. 28. The cardinal view of a laige example. 



Fig. 29. A dorsal view of the same specimen ; the shell has been exfoliated on different parts of the sur- 

 face, presenting the features shown in figure 30. 



Fig. 30. An enlargement of the surface ; showing the tubular charncter of the surface spinules, and, at 

 e, the penetration of these tubes beneath the epidennal layer of the shell. The spinules ai-e 

 represented as simple, short and blunt, but they are, on the contrary, furnished with lows of 

 lateral branches, and are long, slender and acute. 

 Keokuk limestone. Keokuk, lawa. 



