304 MESOZOIC FLORAS OF UNITED STATES. 



1890. Nilssonia cfr. scJiaumhurgensis (Dunk.) Nath.: Denkschr. Wien Akad., Vol. 



LVII, p. 45 [5], pi. i, figs. 6-9, 9a. 

 1898. Angiopteridium strictinerve Font, in Weed & Pirsson: Eighteenth Ann. Rep. 



U. S. Geol. Surv., 1896-97, Ft. Ill, p. 481. (PI: LXXII, Fig. 20.) 



This plant was described by Dunker from the Wealden of northern 

 Germany as Pterophyllum schaumburgense, and he illustrated it bj^ a 

 number of figures showing its variabilit3^ Schimper regarded it as an 

 Anomozamites. In this determination he was followed by Schenk. " 

 Schenk's figures show some variations not seen in those of Dunker and 

 depict some leaves larger than any given by him. Schenk gives as the 

 maximum length of the segments of the leaf 8 mm. 



Nathorst*" gives figures of certain long, narrow cycad leaves from 

 Japan which he correctly regarded as belonging to Bunker's species, but 

 as the segments are inserted on the upper surface of the midrib he held 

 it to be a Nilsonia. Yokoyama*" gives a number of figures of this plant 

 and confirms Nathorst's conclusion as to its character. 



Schenk states that Nilsonia schaumburgensis is the predominant 

 plant in the Wealden of northern Germany. It is found in such numbers 

 in the Geyser beds that it may l^e regarded, if not as the predominant 

 plant there, at least as one of the most important. The specimens 

 yielded by the Geyser beds fully equal in variability those found in 

 Germany and Japan, and the same kinds of variation occur. Any of 

 the forms hitherto figured may be matched in the Geyser fossils. The 

 variations, however, are in nonessential points, such as the length of the 

 leaves, the length and width of the segments, and the shape of the ends 

 of the latter. Notwithstanding this variability the plant is so well 

 characterized that even small fragments of it may be easily recognized. 

 The segments go off normally at nearly or quite right angles with the 

 midrib, but they may curve striately near their ends in a falcate manner 

 toward the end of the leaf. Owing to distortion from pressure, this falcate 

 shape is often exaggerated, and the same distortion tends to sharpen the 

 ends of the segments and to round off in an elliptical form the margin 

 of their ends. They are of nearly or quite the same width from base to 



" Foss. Flor. der Nordwestdeutsch. Wealdenformation, p. 29, pi. xii (Palaeontographica, Vol. XEX, p. 

 231, pi. xxxiii). 



6 Beitriige zur Mesozoiscfaen Flor. .Japans (Denkschr. Wien Akad., Vol. LVII, p. 45), p. 5, pi. i, figs. 6-9a. 



''Mesozoic Plants from Kozuke,etc. (Jour. Coll. Sci. Imp. Univ. Japan, Vol. VII, Pt. Ill, 1894), p. 227, 

 pi. XX, figs, 12, 14; pi. xxi, fig. 14; pi. xxii, figs. 5-7. 



