I'LATH XXXVI— Continued. 



GicNus SPIRIFERINA, dOrbigny. 



I'aRe 51. 



SiMitiFERiNA Kentuckien.sis, Slllllliard. 



Fig'. 14. The extei'ior of a peilicle-valve. 



Fig-. 15. An ol)rKiue vicnv of the interior of tho jieilidfi-valve ; allowing tlie median septum anci mascular 



inipres.sions. 

 Fig. 16. Tlie carilinal view of an exfoliated slieil ; Kliowing- the ch.ai-actoi- of tlie area and deltidial plates. 

 Coal Measures. Illinois. 



Genus SPIKIFEK, .SowEiun-. 



Page 1. 



Spirifeu fimbriatus, Conrad. 

 See Plate 38. 

 Fig. 17. The internal cast of a pedicle-valve ; showing the composition of the muscular ai-ea. 



Schoharie giit. Schoharie, N. Y. 

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

 centrically striated surface covei-ed with the bases of spinules. 

 Upper Helderberg group. Western JS'ew York. 

 Fig. 20. An enlargement of the surface ; showing the bases of the spinules. 

 Fig. 21. A pedicle- valve which retains a portion of the spinules. 



Hamilton group. Western New York. 

 Fig. 22. A cardinal view of an internal cast of conjoined valves; showing the vasculai' sinuses. 

 Hamilton group. Hardy comity, Virginia. 



SpIRIFER PRyEMATURU.S, Hilll. 



Fig. 23. Tlie internal cast of a pedicle-valve, retaining a trace of a median septum. 



Chemung group. Allegany county, N. Y. 

 Fig. 24. The internal cast of a pedicle-valve j showing the impressions of the dental lamella; and a low 



median septum. 

 Fig. [25. Another cast of the pedicle- valve, which i-etains the muscular impression. 



Chemung group. Meadville, Pennsylvania. 



Sfirifer SETIGERUS, Htlll. 



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

 and fimbriated lamellse. 



Chester limestone. Chester, llli7iois. 



SpIRIFER PSEUDOLINEATUS, Hall. 



Fig. 28. The cardinal view of a large 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 chara,cter of the surface spinules, and, at 

 e, the penetration of these tubes beneath the epidermal layer of the shell. The spinules are 

 represented as simple, shoi-t and blunt, but they are, on the contrary, fui'nished with rows of 

 lateral branches, and are long, slen<ler and acute. 

 Keokuk limestone. Keokuk, Iowa. 



