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PLATE n—Continued. 
OBOLELLA, Billings. 
Page 66. 
Obolella crassa, Hall. 
Fig-. 31. The exterior of a valve. Natural size. 
Fig-. 32. The same, enlarged } showing the radiating fetriae betVeeih'the'lainellose growth-lines. X 2. 
Fig. 33. Another valve; similarly ehlarged 1 , in which the 1 radiating" lines do not -appear.' This 1 is the speci¬ 
men originally described as Aviculji dexquaindta,- Hall (Pal. N. Y., vol. i. 1847). 
Fig. 34. The interior iof a pedicle-valve pshowing the'pedicleTgroov.e,".thei cardinal, lateral and central mus¬ 
cular scars. X 2. 
Fig. i' 35. The interior of another^ but smaller; pedicle-valvel;! showing (the same features. X 2. 
Fig. 36.'‘The 1 in tenor of _thb (brachial valve f'showi^g^the' faint 1 pedicle-groOve; the 1 cardinal, external, cen¬ 
tral and laterhl-musC'M&i- iihpf^sibiis 1 . X 2. M " : 
Middle 1 Cambrian .' "Nedr Troy',"N. Y. 
Obolella polita, Hall. 
Fig. 37. The exterior of a valve. X) 4. 
Fig. 38. The interior of a pedicie-valve ; showing the central and lateral muscular impressions. X 2. 
Fig, 39. An.internal cast of tl^e opposit^ (?) valve. X 2. 
Fig. 40. The interior of a ’brachial valve' " X 6'." _ 
Fig. 41. The interior of a pedicle-valve. X .6., 
(Figs. 40 and 41 are from the original drawings.represented in the Sixteenth Kept. N. Y. State 
Cab. Nat: Hist., pi. vi.’figs. 20, 2L) ’ 
Potsd'am’ saridstond. T-rempdleau ,' WU&MHn. 
Obolella gemma, Billings. 
Fig. 42. The exterior of a pedicle-vaive. X 6. 
Fig. 43. (34 in 'error, last line of figures.) The interior of a brachial valve ; showing the muscular im¬ 
pressions. X 6. 
Fig. 44. The interior of a pedicle-valve; showing the Cardinal area, pedicle-groove and muscular im¬ 
pressions. X 6. 
(The originals of figs. 1, 2, 4, 34, 35, 36, 42, 43, 44, are in the collection of Mr. S. W. Ford.) 
