J 



FLOEA OF THE DAKOTA GEOUP. 27 



of the subgenus Lidymosorus, Deb. and Ett., two sori placed upon the 

 middle of the lower pair of veins, one on each side of the medial nerve. 



, The rachis of this fern is described by Heer as slender. As it is figured 

 here it appears somewhat broad, though not larger than it is represented 

 in Heer's "Fl. Arct.," iii, pi. ix, fig. 6. The ultimate rachis is, however, very 

 slender filiform. 



Hah. — Fort Harker, Kansas. Clis. Sternberg. 



LYGODIUM, Sw. 



Liygrodiuin triclioiuauoides, Lesqz. 



"U. S. Geol. Kep.," vi, p. 45, pi. i, fig. 2. 



GYMNOSPERMiE. 



ZAMI^. 



PODOZAMITES, Fr. Br. 



Fronds piunate; leaves distant, obliquely or borizontally attached by an attenuated 

 pedicelliform balf-twisted flat base articulated upon the rachis and therefore caducous; 

 veins equal, longitudinal, converging to both ends of the leaves; borders entire. 



This genus of Braun, as amended by Saporta and Schimper, seems 



adapted for the description of all the leaves of Cycadeae found as yet in 



the Dakota Group. 



Podozamites Haydenii, Lesqx. 



PUrophyllum Haydenii, Lesqx., " U. S. Geol. Rep.," vi, p. 49, pi. i, figs. 6, 66; Hayden's "Ann. Rep.," 1874, p. 334. 



Nothing more definite is known of these vegetable fragments than 

 has been published as quoted above. 



Professor Heer, considering the thickness and impressions of the 

 stems, regards these fragments as more probably referable to Conifers of 

 the section of the Araucarifes than to Cycadem. No leaves of this section, 

 however, can be compared to those which I have figured, and which, by 

 their parallel veins and forms, are very much like the leaves of some 

 species of Podozamites. Indeed, from the remarks on this genus by Heer, 

 the leaves are either narrowed and joined to the stems by decurring to it, 

 or produced into a short pedicel attached to the stem by small tubercles 

 or Avarts. The characters of the genus are thus exactly shown not only 

 by the leaf, but also by the stem whose round small scars indicate points 

 of attachment like tubercles. 



