298 MESOZOIC FLORAS OF UNITED STATES. 



lowest ones in the basal rounded lobes are several times forked and tend to 

 form flabellate bundles, which fill the lobes. 



There is hardly a doubt that this is a species of Cladophlebis distinct 

 from the other species of this genus found in the Geyser beds, and so far as 

 we can judge from so small an amount of material, it is most probably 

 identical with C. constricta of the Virginia Lower Potomac. 



PL LXXI, Fig. 26, gives a representation of this form. 



Order EQUISETALES. 



Family EQUISETACEiE. 



Genus EQUISETUM Linnsus. 



Equisetitm Phillipsii (Dunker) Brongniart . 



PL LXXII, Figs. 1-11. 



184.3. Equisetites PhiUipsii Dunk.: Programni. d. hoheren Gewerbschule in Cassel, 



1843-44, p. 5. 

 1846. Equisetites PhiUipsii Dunk.: Monogr. d. Norddeutsch. Wealdenbildung, p. 2, 



pi. i, fig. 2. 

 1849. Equisetum Phillifsii (Dunk.) Brongn. : Tableau, p. 107. 

 1869. Equisetum Phillipsii (Dunk.) Brongn. Schimper: Pal. Veg., Vol. I, p. 265. 

 1898. Equisetum montanense Font, in Weed & Pirsson: Eighteenth Ann. Rep. U. S. 



Geol. Surv., 1896-97, Pt. Ill, p. 481. (PL LXXII, Fig. 11.) 



The stems of this Equisetum, when of full size, range in diameter 

 from about 15 mm. to 2 cm. Only stems without branches were seen. 

 The dimensions of the sheaths and teeth vary with the size of the stems. 

 Pv,egarding the sheath, as indicated by the strise, it is, in the larger speci- 

 mens, from 15 mm. to 2 cm. long. The internodes in the same average 

 about 3 cm. in length. The teeth in the larger specimens average about 

 6 mm. in length and are 1 mm. wide at base, their widest portion. In form 

 the teeth are narrow lancet-shaped, gradually narrowing from their bases 

 to their tips, where they are acute. Near their margins the teeth are 

 thickened, so that they appear almost as if furnished with lateral keels. 

 The portions of the teeth between these margins are depressed. At their 

 leases on the nodes the teeth are closelj' coherent with the stem, and each 

 one is separated from its neighbors by a sharpl}^ defined furrow, which is 

 widest at the bases of the teeth and narrows down the stem to a mere 



