776 REVIEWS 
botanical details regarding the development of the plant types, their 
relationships, associations, distribution, and so on. With the thorough- 
ness characteristic of his method Berry not only describes all the species 
of fossil plants known from “the lower Cretaceous in Maryland, but, as 
a basis for discussion and comparison, he summarizes all of the known 
lower Cretaceous floras of other parts of the world. ‘The value of the 
latter treatment appears not only in his discussion of the age of the 
American plant beds, but in the broader correlations and in the historical 
outlining of the floras. His correlations show a refinement and precision 
that will surprise many who have not followed the recent studies of the 
Cretaceous floras of the Atlantic coastal plain. As already noted the 
Patuxent-Arundel flora, considered as a whole, is regarded by Berry 
as representing all but the lower portion of the Neocomian together 
with the Barremian. The Patapsco he correlates, on apparently good 
evidence, with the Albian, the Aptian of the old world being represented 
by the hiatus between the Arundel and the Patapsco. It may be noted 
in passing that a surprisingly large number of the previously recorded 
species of the Potomac formation fall into the ranks of synonomy as 
being in Berry’s judgment not well founded. | 
Of the other well-known plant-bearing formations of the older 
Cretaceous in America, the Trinity is considered by Berry as representing 
the Aptian and the upper part of the Barremian. The Lacota forma- 
tion, in the Black Hills, he views as transgressing lower on the Barremian 
and as falling short of the close of the Aptian, thus overlapping on both 
the Trinity and the Arundel, while the Fuson formation of the same 
region falls, he believes, within the Albian, though it is not so early as 
the basal portion of the latter. As already indicated, the Morrison- 
Kootenai beds he treats as probably Cretaceous, in which the Kootenai 
persisted to the close of the Barremian. On the California side the 
Knoxville-Horsetown beds are interpreted by him as reaching without 
break from the top of the Jurassic into the base of the Albian. 
A map shows the distribution in Maryland of the Potomac group, 
the local stratigraphy and areal geology of considerable portions of 
which have previously been represented in greater detail in several 
folios of the U.S. Geological Survey. 
Davip WHITE 
