Mr. L. F. Ward on Mesozoic Dicotyledons. 393 
sists in large part of types represented in the Miocene of 
Europe. 
It thus appears that throughout both hemispheres the con- . 
ditions required for the preservation of vegetable remains in 
Cretaceous time have existed in a marked degree during two 
epochs only, the Cenomanian and the Senonian, separated 
from each other by a period, perhaps equal to either, during 
which marine forms of animal life are chiefly found. <A few 
Dicotyledons only occur in the Turonian of Europe, as e. g. 
Magnolia telonnensis from Toulon, while the Colorado Group 
(Fort Benton, Niobrara) of our Western Territories has thus 
far proved destitute of plant life. 
If now we take up the several subdivisions of the Creta- 
ceous formation in their stratigraphical order, beginning with 
the lowest, we shall see that in the Neocomian, or lowest 
member, no plant-remains of the subclass we have been 
studying have as yet ever been detected *. 
Inthe Urgonian, or next higher group, one species, Populus 
primeva, Heer, has been collected at Pattorfik, in Greenland. 
In volume vi. of his ‘ Flora Fossilis Arctica,’ which appeared 
in 1882 (or eight years subsequent to the original description 
of this plant), Heer continued to adhere to this species as well 
as to its anomalous stratigraphical position. 
The Gault, like the Neocomian, has thus far furnished no 
Dicotyledons, though not always destitute of plant-remains f. 
It is with the Cenomanian that there seems to have burst 
in upon the world a great and luxuriant dicotyledonous 
vegetation. Itis found alike in Saxony, Bohemia, Silesia, 
in Greenland, and in the western United States. Upwards 
of three hundred and fifty species, representing all three of 
the divisions of the subclass (Apetale, Polypetale, Gamo- 
petal), and consisting chiefly of living genera, have been 
described. 
It was formerly supposed that the beds at Blankenburg 
occupied a much lower position than that to which I have 
assigned them, and such as would place them in the Turonian 
at least, if not in the Cenomanian; and Mr. Lesquereux, in 
the large and important work which is about to appear f, 
* The supposed Neocomian Dicotyledons of Russia (Eichwald, ‘ Lethea 
Ressica,’ ii. pp. 58 e¢ seg.) are shown by Heer (Fl. Ross. Arct. iii. Theil 2, 
S. 26) to come from the Lower Senonian corresponding to the Harz 
district. 
+ Heer assigns the plant-beds of Spitzbergen to the Gault (7. c. S. 24), 
and Coemans finds nine new species of fossil plants in the Cretaceous of 
Hainaut (Mém. de lAcad. Royale de Belgique, xxxvi., 1867), which 
Briart and Cornet (J. c. xxxiii. p. 46) placed in the Gault. 
{ “ Cretaceous and Tertiary Floras,” Report of the U.S. Geol. Survey 
of the Territories, vol. viii. (Washington, 1883. 
Ann. & Mag. N. Hist. Ser. 5. Vol. xiii. 26 
