PLATE XXXVII. 



(Figs. 1-14, 28-31 by R. P. Whitfield; 13-15, 18, 19, 23, 24 by E. Emmons; 16, 17, 20-22, 25, 32, 33 by G B. SIMPSON.) 



Genus SPIRIFER, Sowerby. 



Page 1. 



Spirifek Niagakensis, Conrad. 

 See Plate 21. 

 Fig. 1. An enlarged view of the deltidial region of the pedicle-valve ; showing the uncompleted growth 

 of the deltidial plates. 



Niagara shales. Western New York. 



Spikifer NOBiMS, 15;inande. 



Figs. 2, 3. Opposite sides of an internal cast; showing the coarse, duplicating plications, the impressions 

 of strong dental lamellae and a low median ridge in the pedicle-valve. 

 Niagara dolomites. Rcbcitie, Wisconsin. 



Spirifer mesastrialis, Hall. 



Fig. 4. The exterior of a brachial valve, with highly extended cardinal extremities. 



Fig. 5. The brachial valve of a specimen much shorter on the hinge. Both specimens show the fine stiia- 

 tion of the median fold. 



Chemung group. /Southwestern New York. 



Spirifer Tullius, Hall. 



Pigs. 6, 7. Views of an average specimen. The fine radial lineation of the surface is not shown in the 

 figures. 



Hamilton shales. Skaneateles, N. Y. 



Spikifer sculptilis. Hall. 



Fig. 8. Exterior of a pedicle-valve j showing the strong, distant lamellse. 

 Hamilton group. Western New Ym-k. 



Spirifer consobrinus d'Oil)igiiy (=S. zic-zac. Hall). 



See Plate 34. 

 Figs. 9, 10. Views of both valves of a normal example ; showing the sharp plications and the closely 

 crowded concentric lamelliE. 



Hamilton group. Canandaigua Lake, N. Y. 



Spirifer gregarids, Clapp. 



Figs. 11, 12. Two views of an average specimen ; showing the short hinge, prominent umbo, and the broad, 

 deep sinus of the pedicle-valve. 



Corniferous limestone. Falls of the Ohio. 



Spirifer Keokuk, Htill, var. ? 



Pigs. 13-15. Views of a silicitied shell, with sharp lateral plications, and low duplicate median plications on 

 the fold and sinus. 



St. Louis group. Southern Indiana 1 



Spirifer Texanus. Meek. 

 Figs. 16, 17. Views of a rather small specimen'; showing the shiirt hinge, elongate form and highly arched 

 umbo of the pedicle-valve. 



Carboniferous limestone. Qrdham comity, Texas. 



