294 MESOZOIC I LOKAS OF UNITED STATES. 



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

 ment of a fern which, from its Xeuropteris-like nervation, was su])posed to 

 Ije pi'obalily a new Thinnfeldia. In the previously mentioned picliminary 

 report the pi'ovisional name T. monlaticrif^ifi was proi:)ose(l foi' it. In 

 Professor Ward's collection the numl)er of lai'gei- and much hettei' pre- 

 served specimens of this j)lant obtained show that this is a variety of 

 Cladophlehiti f(iU-at(t . This specimen is I'epresentcMl on PI. LXXI. Fig. 20. 



('LAnopni-Eius iiETEKopini.i.A Fontaine. 



PI. LXXI. Fig.s. 21-L>5. 



1S92. CladofhleUs heterophylla Funt.: Proc. U. S. Xat. Mu.s., Yo[. XV, p. 493, 

 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 (Jreat 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," puljhshed l)y the X^ational Museum, Vol. X^^ 

 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 scant}' 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, by 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 clearly exhil)ited in some of the Geyser specimens. 

 Xone of the forms from the Geyser locahty show the diminution of the 

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

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

 specific character. This must accordingly be regarded as a distoi-tion due 

 to some local cause. 



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

 that the fern showed some varialiility in the noi-mal or common pinnules. 

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



