2 THE LATER EXTINCT FLORAS OF NORTH AMERICA. 



to contraction in drying before they were submerged and how much is 

 natural it is now impossible to say; but specimens from Currant Creek, 

 Oregon, exhibit the same peculiarity, the lobes being sometimes almost 

 fan-shaped, the margins waved or involute, and recalling by their mode of 

 growth the fronds of Marchantia, repeating what is so conspicuous in the 

 Green River shales. We must therefore regard the characters enumerated 

 as normal. 



The nervation is in most specimens clearly defined and rather strong. 

 It is crowded as compared with that of some other species, and is confluent 

 along the middle of the lobes, precisely as in Neuropteris, without producing 

 a midrib. 



Professor Heer has described and figured in his great work on the 

 plants of the Swiss Tertiaries (Fl. Tert. Helv, Vol. I, p. 42, PI. XIII, fig. 

 3, and Vol. Ill, PL CXVII, fig. 25b) a species of Lygodium which evi- 

 dently closely resembles this; so much so that unless some distinctive char- 

 acters are furnished by the lobing of the fronds, they are likely to prove 

 identical. Professor Heer names his species L. acutangulmn, from the nerva- 

 tion, which is identical with that of the Green River specimens, but he 

 describes the frond as three-lobed His specimens are, however, very 

 imperfect, and two or three lobed specimens could be selected from the 

 suite before me which would, taken by themselves, require a description 

 corresponding precisely with that given by Heer. 



Among the fronds collected by Dr. White at Green Rh'er is one which 

 has much narrower lobes than the others, and it has apparently a finer 

 nervation; but it is unfortunately much weathered, and the details of struc- 

 ture are rendered obscure. A figure is now given of it (PL LXII, fig. 2), 

 but I am inclined to regard it as only one of the many forms of one protean 

 species. 



Since the above notes were written Messrs. Gardner and Ettingshausen 

 have published their Monograph of the British Eocene Flora, Vol. I, Filices, 

 and on PL VII have given a number of figures of Lygodium Kaulfussi Heer, 

 with which they identify Lesquereux's species; a conclusion to which he 

 also subscribes. It will be seen, however, by a comparison of Lesque- 

 reux's figures with those now given and with those published by Heer and 

 Gardner that the American fern had larger pinnae with broader and less 

 undulate lobes, which are nearly of the same breadth from base to summit. 



