PLATE XXXVU— Coutinaed. 



Spiuifer ForbI'ISI. Norwood and Piattci). 



Fi^. 18. An eiilargeii view of the caiiiinal aroa of the pedicle valve, from which the surface layer has been 

 partially exfoliated, exposing the vertical canals traversing the shell-substance. 

 Burlington limestone. Burlington, Iowa. 



Spirifer lateralis. Hall. 



See Plate 32. 

 Fig. 19. An enl&i-gement of the cardinal area, showing features similar to the preceding. 

 Warsaw group. Cl\fton, Illinois. 



Spirifer Williamsi, sp. iiov. 



Figs. 20-22. Views of an enlarged example ; showing the low, coai-se and Hparpe plication of the median 

 fold and sinus. 



Chemting group. Allegany county, N. Y. 



Spirifer Canandaiou^, sj). iiov. 



Figs. 23, 24. Two ^^ew8 of a somewhat distorted individual ; showing the low, rounded lateral plications 



and naiTow umbo. 

 Fig. 25. An enlargement of the sui-face j showing the closely crowded concentric rows of fine granules or 



spine-bases. X u. 



Hamilton shales. Canandaigua Lake, N. T. 



Spirifer Hungerfordi, Hall. 



Figs. 26, 27. Doi'sal and profile views of a specimen with elongate outline and short hinge. 



Fig. 28. Anterior view of the same individual ; showing the development of the median fold and sinus. 



Fig. 29. A shell with an extended hinge-line and short longitudinal axis ; pi-esenting the extreme of varia- 

 tion in this respect. 



Fig. 30. The central portion of the interior of a pedicle-valve ; showing the teeth, dental lamellse and mus- 

 cular impressions. X 2. 



Upper Devonian. Bockford, Iowa. 



Spirifer plenus, Hall. 



See Geol. Rept. of Iowa, p. 603, pi. xiii. 1858. 

 Fig. 32. An enlargement of a poi-lion of the inner surface of the shell ; showing the punctse. X 4. 

 Fig. 33. A jjortion of the external surface near the anterior margin. X 6. 

 Burlingfton limestone. Burlington, Iowa. 



