90 MESOZOIC FLORAS OF UNITED STATES. 



branch near the ends of the pinnule is a noteworth}- feature. The general 

 aspect of the plant is that of a cycad, and it is Idv no means certain that it 

 is not one." 



Pl. XVI, Fig. 1, gives the only specimen seen, and Fig. 2 an enlarge- 

 ment of the same to show the details of nervation. 



Genus NILSONIA Brongniart. 



As stated under the head of Tseniopteris, there are in the Oregon 

 Jurassic certain taniopteroid forms, which, although constantly without 

 segmentation, must be placed with Nilsonia, l:>ecause the lamina is inserted 

 on the upper face of the midrib. In place of the midrib, when the upper 

 surface is presented uppermost, they show a cord in which the bases of the 

 lateral nerves on each side of the midrib are inserted. When, however, 

 the upper face is downward a midrib is visible. The plants have a rather 

 well-defined character. The leaves were mostly thin and easily lacerated 

 or puckered, giving sometimes a deceptive appearance of original segmen- 

 tation. The lateral nerves are single, parallel, of equal strength from 

 base to end, go off nearly at a right angle, and curve slightly toward the 

 ends of the leaves. They thus contrast strongly with the true Tseniopte- 

 rids. These unsegmented Nilsonias are the most abundant ones in the 

 Oregon Jurassic, far surpassing the segmented forms. 



Nilsonia orientalis Heer. 



PI. XVI, Figs. .3-9. 



1878. Nilsonia orientalis Heer: Fl. Foss. Arct., Vol. V, Pt. II (Beitr. Foss. Fl. 

 Sibiriens), p. 18, pl. iv, figs. 5-9. 



Heer has described as Nilsonia orientalis a fossil that is evidently the 

 same as a plant that is quite widely distributed in the Oregon Jurassic. 

 He indicates segmentation in some of his forms, but it may be that this is 

 accidental and due to imperfect preservation. The Oregon specimens are 

 aU without original segmentation, but, from mutilation, sometimes show 

 what looks like it. There are apparently in the Oregon fossils two varie- 

 ties, one the type of the species and the other a smaller form, which may 



"Mr. Seward (Jur. Fl. Yorksh. Coast, p. 238) refers all these forms to Ptilozamiies (Ctenozamites) Leck- 

 enbyi (Bean) Nath., and regards them as cycadaceous. They certainly simulate ferns in many respects, and 

 it is proper that they stand first as being lowest in the grand division of seed-bearing plants.— L. F. W. 



