DESCllIPTIOISr OF SPECIES. PP. 89 



The pinn?e of the ultimate order in this plant were very 

 long, for we have seen them incomplete and yet more than 

 a foot in length. They must also have been very decidu- 

 ous, for we find almost always only, detached pinnae. They 

 lie by thousands in the shale, forming often all the plants 

 found in a particular layer. 



The distribution of this plant is very peculiar at Cass- 

 ville where it occurs. The Waynesburg Coal is divided 

 into three benches, by two partings of shale, one near the 

 middle and the other near the top of the bed, and above 

 this last or second parting there is usually about 12 inches 

 of coal. In the shale under this top or " roof coal," is the 

 habitat of our plant. The shale itself is usually about 12 

 inches thick, of line grain and well adapted to the preser- 

 vation of plants. 



The Alethopteris occupies this shale, and excludes al- 

 most entirely all other plants. Above the "roof -coal," in 

 the roof-shales, where we find nearly all our other plants 

 from this locality, we never find the Alethopteris, either 

 here or elsewhere. It seems extinguished in the subsidence 

 causing the deposit of this shale. The plant is very poly- 

 morphous, so much so indeed, that but for the abundant 

 material afforded, which enables us to obtain a number of 

 intermediate forms, we would have been tempted to form 

 several species out of this one. Fig. 1, PI. XXXIII, gives 

 an enlarged form of the pinnules with swellings at the base, 

 which we take for fructifications. Prof. Lesquereux, in the 

 Illinois Report, Vol. IV, PI. 10, Fig. 6, gives a similar form 

 of fructification, as shown in his Alethopteris injlata. 



Aletliopteris gigas, Gein. Plate XXXIII, Figs. 5 and 6. 



We give on PL XXXIII, in Figs. 5 and 6, a representation 

 of a plant which in its general appearance cannot be distin- 

 guished from A. gigas, Gein. It has the same shaped pin- 

 nules, the same large and swollen looking mid-nerve of the 

 pinnules, and the same general facies. The plant is found 

 only in sandy shale, which does not x>i"eserve its lateral 

 nerves, hence we cannot identify it positively with Geinitz's 

 plant. 



