608 THE AMERICAN NATURALIST. (VoL. XXXV. 
An examination of extra-British Jurassic plants presents in con- 
venient form an approximate comparison of the Jurassic floras of 
the various countries of the world, and the probable identity of such 
species with, or their resemblance to, British types is made clear by 
the use of a tabular presentation. 
The present studies offered some conclusions of interest, of which 
the following may be noted : 
The Jurassic flora shows a great preponderance of ferns and cycads, 
with relatively few conifers, and a remarkable paucity of the Equise- 
tales and Bryophyta, in all of which features it exhibits a striking 
similarity to the flora of the Wealden as described in previous 
British museum catalogues, while they appear to be directly con- 
nected by a few apparently identical species, such as JMafonidium 
gepperti, Ruffordia gepperti, and Ginkgo digitata, which are common 
to both floras. ; 
Among the Equisetales the generally large size of the stems indi- 
cates a much nearer approach to the arborescent forms of the Tri- 
assic and Paleozoic than to the diminutive representatives found 
among the modern horsetails. In Æguäsetites columnaris, which is 
one of the most common and characteristic plants of the Yorkshire 
flora, the author finds evidence that the small'seams of coal which 
occur in strata of the Estuarine series, were formed in part, if not 
entirely, from the remains of the Equisetaceous plants which flour- 
ished in the Jurassic swamps. - | 
Ferns of the Sagenopteris and Cladophlebis types, while often 
abundant, afford little satisfactory evidence of relationship, which 1s 
much more clearly indicated by the Matoninez and Dipteridinz, 
which were abundantly represented in Jurassic time, and also by the 
Osmundacez and Cyatheacez. The Schizeaceze were also repre 
sented by a few doubtful examples, but the Gleicheniacez and the 
Marattiacee are as yet unknown elements in the Yorkshire coast 
flora. From the types so far recognized it appears that this flora 
finds its closest resemblances among existing species in the Southern 
Hemisphere, where the Malayan Matonia pectinata, the Asiatic Dip- 
teris, Dicksonia arborescens of St. Helena, and Zodea barbara of New 
Zealand and Australia offer the closest parallelisms. b 
Among the Ginkgoales, both Ginkgo and Baiera are characteristic 
of the Jurassic floras, and they appear to have extended bac 
through the Triassic into the Permian. Their extreme northern 
Tange points with considerable force to a vigorous development x 
the Ginkgoales during later Mesozoic time. 
