PLATE XXXVII—Continued. 
SriRiFER Forbksi. Norwood uiid Piiitteii. 
Fig. 18. An enlarged view of the cardinal area of the jiedicle-valve, fi'om which the surface layer has been 
partially exfoliated, exposing the vertical canids traversing the shell-substance. 
Burlington limestone. Burlington, Iowa. 
Spirifer lateralis. Hall. 
See Plate 32. 
Fig. 19. An enlargement of the cai'dinal area, showing features similar to the pi'eceding. 
Warsaw group. Clifton, Illinois. 
Spirifer Wir-LTAMSi, sp. nov. 
Figs. 20-22. Views of an enlarged example; showing the low, coarse and .‘•parse jilication of the median 
fold and sinus. 
Chemung grouj:). Allegany county, N. Y. 
Spirifer Canandaigu/E, sp. iiov. 
Figs. 23, 24. Two views of a somewhat distorted individual; showing the low, rounded lateral plications 
and narrow umbo. 
Fig. 25. An enlargement of the surface ; showing the closely ci-owded concentric rows of fine gi'annles or 
spine-bases. X 5. 
Hamilton shales. Canandaigua Lake, N. Y. 
Spirifer Hungerfordi, Httll. 
Figs. 26, 27. Dorsal and profile views of a specimen with elongate outline and short hinge. 
Fig. 28. Antei'ior 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; presenting the extreme of varia¬ 
tion in this respect. 
Fig. 30. The central portion of the intei-ior of a pedicle-valve ; showing the teeth, dental lamellse and mus¬ 
cular imju’essions. X 2. 
Upper Devonian. Rockford, Iowa. 
Spirifer plenus, Hal I. 
See Geol. Kept, of Iowa, p. 603, pi. xiii. 1858. 
Fig. 32. An enlargement of a portion of the inner surface of the shell; showing- the punctse. X 4. 
Fig, 33. A portion of the external surface near the anterioi- mai-gin. X 6. 
Bui-lington limestone. Burlington, Iowa. 
