136 HISTORICAL PALEONTOLOGY. 



" 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 palaeontological, 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 life of the Devonian period, we are now 

 acquainted with a large and abundant terrestrial flora this 

 being the first time that we have met with a land vegetation 

 capable of reconstruction in any fulness. By the researches 

 of Gceppert, 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 

 (Pecopteris, Neuropteris, Aleihopteris, Sphenoptcris, &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 Lepido- 

 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 

 (LycopodiacecE] ; the Calamites are equally gigantic Horse-tails 

 (Equisetacecz) ; 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 



