459 
from the oldest tertiary of Sézanne ; MZ. gracilis Sap.,2 allied to M. 
4imealis Lindl., also from Sézanne; MJ. sinuatus Sap.3 from the 
Miocene of Marseilles; JZ. dichtyophylla Sap.,* from Aix, France ; 
Marchantites oolithicus Fliche’ from the Lower Oolite of the 
vicinity of Nancy, France; and the recently described’ Marchan- 
lites Zeilleri Seward,$ from the English Wealden. It is therefore 
interesting to find that this group of plants was early in existence 
in America as well as in Europe. 
This new American species is regarded as being allied to the 
genus Preissia, and I have made a new genus for its reception by 
the addition to the name ofthe living genus of the termination -z/es 
to indicate its fossil: state; yet it is with a good deal of hesitation 
that it is referred to this rather than to the evidently allied genus 
Marchantia. But taking Marchantia polymorpha as the type, very 
little can be found in the coarser structure of its thallus that would 
be likely, if it were fossilized, to give rise to the regular vein-like 
lines so prominent in the fossil form under consideration. On the 
other hand, the thallus of Preissia commutata is provided on the 
under side with scales that would be very likely to be preserved as 
lines if it should become fossilized. In the absence of fruit, how- 
€ver, it is unsafe to attempt positive conclusions on a purely 
vegetative character, and this determination is to be regarded as 
tentative. : 
In the accompanying figures (Plate 219, Figs. 1 and 2) the 
lines along the midvein appear stronger than they really are, 
and might easily be mistaken for veins. Their true nature is 
better shown in Fig. 3, where they are drawn as overlapping 
Scales. The specimens are small, not especially well preseved and 
hence in the drawings these lines are rather more prominent than 
they should be. 
The Specimens of this hepatic, all of which are figured, were 
collected by Prof. Lester F. Ward, of the U. S. Geological Survey, 
August 3-7, 1883, at Burns’s Ranche, on the Lower Yellowstone, 
Suede ne 
*Op. cit. 312, 2. 7, Fig. 9. cee 
i : Sci. Nat. Bot. (V.) 3: 68, a fe: ed 
. CIE IF: A : . 
+ Bull d. Scene ee . a Mee ‘inaee Sib. ty TEC 1882): : 
* Cat. Mesoz, Pl. Brit, Mus., Wealden Flora Pt. i. 18, 07. 7, /ig- 3. Pane 
