96 MESOZOIC FLORAS OF UNITED STATES. 



NiLSONiA PTEEOPHTLLOiDES Nathopst non Yokoyama. 

 PI. XVIII. 



1878. Nilssonia pterophi/IIoides Nath. [non Yok."]: Foss. FI. vid Bjuf, Hft. I, 



p. 11 (nomen). 



1879. Nilssonia pterophylloides Nath. [non Yok.]: op. cit., Hft. II, p. 72, pi. xvi, 



fig. 1; pi. xvii, figs. 2, 3. 



Several specimens of a plant were obtained from the Oregon Jurassic 

 strata that seems to be identical with the Nilsonia pterophylloides of 

 Nathorst, occurring in the Rhetic of Sweden. Nathorst's forms, how- 

 ever, seem to be rather larger than those from Oregon. Yokoyama 

 has described from Japan, with the name Dioonites Kotoei,'' a similar 

 form, which, although smaller than the Oregon type, seems to be essen- 

 tially the same and to be a Nilsonia rather than a Dioonites. It is true 

 that Nathorst shows his leaflets as going off at an acute angle, whereas 

 the Oregon forms have leaflets that are inserted at nearly or quite a 

 right angle. But all of these are distorted, and the true angle of inser- 

 tion may be diffei'ent, or Nathorst's plants may show the leaflets of 

 the upper part of the leaf, while in the Oregon specimens they may 

 belong to the lower portions, where, as is common in segmented leaves 

 of this type, the segments make a larger angle with the axis than they 

 do in parts nearer the ends of the leaves. Only fragments of leaves, 

 rather poorly preserved, were obtained. Judging from the specimens, 

 the leaflets were inserted by the entire, not widened, bases of the upper 

 face of the axis. They are linear in form, widest in the lower portion, 

 and narrowing gradually toward the end. The ends in no case were 

 preserved, so that their true nature can not be determined, and their 

 full length is not known. The leaf texture seems to have been thin. 

 In some of the specimens; owing to distortion just above the bases of 

 the leaflets, the bases appear widefied. The greatest length of leaflet 

 seen is 65 mm., the tips not being preserved. The width near the base 

 of the widest leaflet is 5 mm. The nerves are about 7 in number. They 

 are inserted at the same angle as the leaflets, are single, and of equal 



« Yokoyama in 1894 named a form from the Mesozoic of Japan Nilssonia pterophylloides as a new species 

 (Journ. Coll. Sci. Imp. Univ. Japan, Vol. VII, Pt. Ill, 1894, pp. 207, 228, pi. xxii, figs. 8-10; pi. xxv, fig. 7). 

 It proves to be the Nilsonia calijomica Font, of the Shasta group. See p. 252. — L. F. W. 



6 Journ. Coll. Sci. Imp. Univ. Japan, Vol. Ill, Pt. I, pp. 44-45, pi. vii, figs, labc, le; pi. xiv, fig. 14. 



