158 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



of the largest thalli showing three such branches. The carbonaceous 

 matter has come off over the " midrib," showing it to be broad and 

 diffuse, this being a well-known character of the living Mar chant hi. 

 The obliquely disposed bundles of rhizoids, which, as already stated, 

 somewhat simulate veins, are exactly paralleled in many well pre- 

 served specimens of M. polymorpha in the herbarium of the U. S. 

 National Museum. One thing which may militate against its refer- 

 ence to Marchantia is the absence of the fine areolations which are so 

 conspicuous in the thallus of the living species. Otherwise it is so 

 close to the living M . polymorpha as to preclude the propriety of re- 

 ferring it to other than the living genus. It is entirely possible that 

 subsequent exploration in the beds whence it came may disclose the 

 presence of fruit, but until such is discovered its relation may remain 

 as above set forth. 



So far as T know only two species of Hepaticae have previously been 

 reported in a fossil state in this country, though specimens of the liv- 

 ing Marchantia polymorpha have been found in calcareous tuff, evi- 

 dently of recent age. The oldest of these is a doubtful specimen from 

 the Jurassic beds of Douglas County, Oregon, referred by Fontaine a 

 to Marchantites erectus (Bean) Seward, but it is very unlike the 

 present species, and it is doubtful if it is properly referred to the 

 Hepatica 3 . 



The other form is Preissites wardii Knowlton, 6 found in beds of 

 the same age as the form under discussion, and coming from Burns's 

 Ranch on the lower Yellowstone, 30 miles below Glendive, Montana. 

 Preissites wardii is a much smaller species than M. pealci, the ex- 

 tremes of size as observed being a length of from 8 to 15 mm. and a 

 width <>f about G mm. It strongly suggested the living Marchantia 

 polymorpha, but on account of the presence of prominent vein-like 

 lines nearly at right angles to the midrib it was thought to be prob- 

 ably most closely related to the living genus Preissia. In this genus 

 the under side of the thallus is provided with scales which it was 

 thought might appear as lines if fossilized. The vein-like lines are 

 present in M. pealei, but they are clearly due, as already explained, 

 to bundles of rhizoids and not to ventral scales. It is possible, 

 however, that with further material of both forms the supposed 

 generic lines might break down, but specifically they would differ in 

 the smaller size and different mode of branching in P. wardii. 



A form that is very much closer to M. pcalei is Marchantia sezan- 

 nensis Brongniart, which was found by Saporta c so well preserved 



" Fontaine in Ward, U. S. Geol. Surv., Mon. 4s, 1905, p. 52. pi. vn, figs, 1, 2. 



* Bull. Torr. Bot. Club, XXI, 1S94, p. 45S, pi. ccxix. 



'Mem. Soc. Geol. d. France, 2 ser., VII, 1S68, p. 30S, pi. xxn, figs. 1-8. 



