136 HISTORICAL PALAZZAONTOLOGY. 
“* Catskill Group”—which pass conformably upwards into the 
Carboniferous, and which may perhaps be regarded as the 
equivalent of the great sandstones of the Upper Old Red in 
Scotland. 
Throughout the entire series of Devonian deposits in North 
America no unconformability or physical break of any kind 
has hitherto been detected ; nor is there any marked interrup- 
tion to the-current of life, though each subdivision of the series 
has its own fossils. No completely natural line can thus be 
indicated, dividing the Devonian in this region from the Silu- 
rian on the one hand, and the Carboniferous on the other 
hand. At the same time, there is the most ample evidence, 
both stratigraphical and paleontological, as to the complete 
independence of the American Devonian series as a distinct 
life-system between the older Silurian and the later Carbon- 
iferous. The subjoined section (fig. 76) shows diagrammati- 
cally the general succession of the Devonian rocks of North 
America. 
As regards the “/e of the Devonian period, we are now 
acquainted with a large and abundant terrestrial /7ora—this 
being the first time that we have met with a land vegetation 
capable of reconstruction in any fulness. By the researches 
of Goeppert, Unger, Dawson, Carruthers, and other botanists, 
a knowledge has been acquired of a large number of Devonian 
plants, only a few of which can be noticed here. As might 
have been anticipated, the greater number of the vegetable 
remains of this period have been obtained from such shallow- 
water deposits as the Old Red Sandstone proper and the Gaspe 
series of North America, and few traces of plant-life occur in 
the strictly marine sediments. Apart from numerous remains, 
mostly of a problematical nature, referred to the comprehensive 
group of the Sea-weeds, a large number of Ferns have now 
been recognised, some being of the ordinary plant-like type 
(Pecopterts, Neuropteris, Alethopteris, Sphenopteris, &c.), whilst 
others belong to the gigantic group of the “ Tree - ferns” 
(Psaronius, Caulopteris, &c.) Besides these there is an abun- 
dant development of the singular extinct types of the Zefzdo- 
dendroids, the Sigillarioids, and the Calamites, all of which 
attained their maximum in the Carboniferous. Of these, the 
Lepidodendra may be regarded as gigantic, tree-like Club-mosses 
(Lycopodiacee) ; the Calamites are equally gigantic Horse-tails 
(Lquisetacee); and the Sigillarioids, equally huge in size, in 
some respects hold a position intermediate between the Club- 
mosses and the Pines (Conifers). ‘The Devonian rocks have 
