y 



PLANTS FROM ALASKA. 157 



toward the ends of the ultimate pinnae and are more and more united, 

 so that they pass to lobes and finall_y to teeth. The obliquity of insertion 

 of the pinnules makes the bases of the ultimate pinnae wedge shaped. 

 Toward the termination of the compound pinna, or frond, the ultimate 

 pinnse become reduced to pinnules. In such parts the penultimate 

 pinnse, now reduced to ultimate ones, are much elongated and toward 

 their ends have the pinnules passing into lobes and finally into teeth. 

 Toward the ends of the compound pinna the ultimate pinnse become 

 reduced to elongate dentate pinnules. The same obliquity, narrowness, 

 and acuteness are maintained in these transformations into lobes and 

 teeth. The nervation can not be made out, as all the specimens are 

 preserved in a sandstone. No fructification is shown, and the plant must 

 be determined from the character of its sterile parts. It differs somewhat 

 from the • character of Onychiopsis psilotoides as given in most of the 

 specimens hitherto described, but the variation does not appear greater 

 than the limits of the species. The variation is found in the facts that 

 the Alaskan fossil has the pinnules, lobes, and teeth more closety placed 

 than in most of the forms of 0. psilotoides and that the laminse of the 

 foliage is in greater proportion to the nervation. The crowding may be 

 due to a creep of the rock and to pressure, for these features appear in 

 the specimens. 



This plant resembles 0. elongata (Geyl.) Yok., a Jurassic fossil, but 

 is more dehcately incised. It probably lies between it and 0. psilotoides. 

 It is also near a number of fossils described in Monogr. U. S. Geol. 

 Surv., Vol. XV (The Potomac or Younger Mesozoic flora). It especially 

 resembles Thyrsopteris angustifolia Font., the form given in Fig. 8 being 

 much like those depicted in that work on pi. xlv, fig. 3, and pi. xlviii, 

 fig. 2. But the pinnules and lobes of the Alaskan plant are more slender 

 than even these. 



Genus CLADOPHLEBIS Brongniart. 



Cladophlebis vaccensis Ward." 



PI. XXXIX, Pigs. 7, 8. 



1888. IPecopteris denticulata Heer. Lesquereux: Proc. U. S. Nat. Mus., Vol. XI, 

 p. 32. 



On one of the rock fragments collected by Mr. Woolfe there is an 

 imprint of fern which has the Museum No. 2526 and Professor Lesque- 



" See pp. 66-6S. 



