1864. | Botany and Vegetable Physiology. 455 
which is the boulder drift. It isin the fine and soft mud, at from 
1 to 4 inches below the surface, beneath and immediately around the 
waters of the pond, that the siliceous remains of the new species are 
most abundant. The gathering is principally remarkable for two 
points :—1l. The striking analogy which exists between its species and 
those of the sub-peat deposits of the northern section of the United 
States. 2. The occurrence of several forms belonging to a known 
genus Surirella, so peculiar and variable in their characters as 
almost to merit the title of transitionary, by which is meant that 
these forms may be regarded as just such aberrant varieties of that 
genus, as we might expect to find conducting to the genera Nitzschia 
and Synedra, which in America seem to have followed the genus 
Surirella, at a long interval of time. They exhibit, moreover, such 
very unusual variation as to size, configuration, and definition of dis- 
tinctive characters,—such want of generic fixity—as might be supposed 
likely to mark the incoming of new genera. Dr. Lewis describes the 
following new species :—Surirella Baileyi, S. intermedia, and var, 
S. anceps, S. delicatissima, Actinella punctata, Tryblionella or Denticula, 
n. sp. Amphora intermedia, Navicula, n. sp., Mastogloia elegans, Amphi- 
prora pulchra, var. 8, which seems to be A. conspicua of Greville. 
Principal Dawson has examined the Flora of the Devonian period, 
of North-east America, and he comes to the following conclusions :— 
1. In its general character the Devonian Flora resembles that. 
of the carboniferous epoch in the prevalence of Gymnosperms and 
Cryptogams ; and, with few exceptions, the generic types of the two 
periods are the same. 
2. Some species which appear early in the Devonian period con- 
tinue to its close without entering the carboniferous; and the greater 
majority of the species even of the upper Devonian, do not reappear 
in the carboniferous period, but a few species extend from the upper 
Devonian to the lower carboniferous, and thus establish a real passage 
from the earlier to the later Flora. 
3. A large part of the difference between the Devonian and car- 
boniferous Floras is probably due to different geographical conditions. 
The wide, swampy flats of the coal period do not seem to have existed 
in the Devonian era. The land was probably less extensive, and 
more of an upland character. On the other hand, we find that the 
beds of the Middle Devonian, similar to the underclays of the coal 
measures, are filled, not with Stigmaria, but with rhizomes of Psilo- 
phyton. 
4. The conditions in the Devonian period seem to have been less 
favourable to the preservation of plants than those of the coal epoch. 
5. The Devonian Flora was not of a lower grade than that of the 
coal period, 
6. The general character of the Devonian Flora, in America, is 
very similar to that of the same period in Europe. Yet the number 
of identical species does not seem to be so great as in the coal-fields 
of the two continents. 
In a paper on the coal formation of North America, given in the 
