64 FLORA OF LOWER COAL MEASURES OF MISSOURL 



Sorodaclus deserve a detailed description along with other material coin- 

 prising fertile ferns from the American Coal Measures. 



Localities. — The sterile forms come from Pitcher's coal bank, U. S. 

 Nat. Mus., 5536, 5698. The original specimens of Sorodadus opliioglossoides 

 Lx. from Henry County, without more exact locality, are Nos. 1227 and 4272 

 of the Lacoe collection, U. S. Nat. Miis. 



Sphenopteris subceenulata (Lx.). 

 PI. XX, Fig. 5. 



1866. Alethopteris crenulata (Brongu.) Goepp., Lesquereux, Rept. Geol. Surv. Illinois, 



voL ii, p. 439, pi. xxxix, figs. 2-4. 

 1870. Alethopteris crenulata (Brongn.) Goepp., Lesquereux, Rept. Geol. Surv. Illiuois, 



vol. iv, p. 393, pi. xiii, figs. 14, 15. 

 1879. Pseudopecopteris subcrenidata Lesquereux, Coal Flora, Atlas, p. 6, pi. xxxvii, 



figs. 7, 8; text, vol. i (1880), p. 193. 



The specimen figured in PI. XX, Fig. 5, agrees in so man}^ respects 

 with several examples from Cannelton, Pennsylvania, and Mazon Creek, 

 Illinois, labeled Pseudopecopteris suhcrenulata by Professor Lesquereux, as 

 to leave little doubt as to its proper inclusion in that somewliat variable 

 species. The lamina of the pinnules is thin, though minutely rugose, with 

 the margins more or less distinctly retracted between the tips of the 

 nerves, the crenulation being less marked on the sides than near the apex 

 of the pinnules. The nerves, which in the specimen in hand are viewed 

 from the back side of the frond, are clear and in relief The midrib is 

 rather slender and decurrent, the nervils pinnate, for the most part nearly 

 straight and very oblique. The nervils are themselves striate, often 

 appearing double, as is the case in the specimens from Mazon Creek. 



The specimens from Illinois and Pennsylvania, referred to above, rep- 

 resent a form similar to that given in fig. 8, pi. xxxvii, of the Coal Flora. 

 It would seem at first that this should be quite distinct from the type illus- 

 trated in fig. 7 of the same plate. But the variation in the size and nerva- 

 tion in the entire suite of specimens from Mazon Creek is, as Professor 

 Lesquereux remarked,^ so great that it is difficult to establish any satisfac- 

 tory line of demarcation among them, although more than one species 

 seems to be represented. In the specimen from Missouri the two or three 



1 Coal Flora, vol. i, p. 193. 



