294 MESOZOIC FLORAS OF UNITED STATES. 



In Mr. Weed's collection there was an imperfecth^ preserved frag- 

 ment of a fern which, from its Neuropteris-like nervation, was supposed to 

 be probably a new Thinnfeldia. In the previously mentioned preliminary 

 report the provisional name T. vionta7\ensis was proposed for it. In 

 Professor Ward's collection the number of larger and much better pre- 

 served specimens of this plant obtained show that this is a variety of 

 Cladophlebisfalcata. This specimen is represented on PL LXXI, Fig. 20. 



Cladophlebis heterophylla Fontaine. 



PI. LXXI, Figs. 21-2.5. 



1892. CladophleUs TiMerojyhyUa Font.: Proc. U. S. Nat. Mus., Vol. XV, p. 49.3, 

 pi. Ixxxiv, fig. 2. 



A considerable number of specimens of a small fern were found in the 

 Gej'ser beds which appears to be identical with Cladophlebis heterophylla 

 Font. This was found in two small and rather imperfect specimens in the 

 strata of the Great Falls coal field of Montana, and was described by me 

 in a paper entitled ' ' Description of some Fossil Plants from the Great Falls 

 Coal Field of Montana, ' ' published by the National Museum, Vol. XV, 

 pp. 487-495, with plates Ixxxii-lxxxiv. The description is given on page 

 493, and the plant, so far as then known, is figured on pi. Ixxxiv, fig. 2. 

 In the description it was stated that the full character could not be made 

 out owing to the imperfect and scanty material. In the Geyser beds a 

 considerable number of specimens were found. Some of these are much 

 larger than those from Great Falls and better preserved, so that they 

 show more of the nature of the plant. At the same time, bj' taking 

 specimens from different parts of the plant its character can be better 

 made out. The nervation was shown only vaguely in the fossils from 

 Great Falls, while it is clearlj- exhibited in some of the Geyser specimens. 

 None of the forms from the Geyser locality show the diminution of the 

 ultimate pinna toward the base of the primary pinnae which is seen in the 

 Great Falls fossil, and which was taken as one of the features forming its 

 specific character. This must accordingly be regarded as a distortion due 

 to some local cause. 



Again, in the more numerous forms from Geyser we are enabled to see 

 that the fern showed some variability in the normal or common pinnules. 

 The inferior pinnule, however, at the base of each ultimate pinna, next to 



