PALEOZOIC TIME — DEVONIAN. 576 



DEVONIAN ERA. 



Synonymy. — Old Red Sandstone Series (from the rocks in Scotland), British Geologists 

 before 1839. Devonian system, Sedgwick and Murchison, in a paper on the Classification 

 of the older rocks of Devonshire and Cornvi^all, Ann. Phil, April, 1839. Old Red Sand- 

 stone, or Devonian system, Lyell, Elements of GeoL, 1841. Devonian, of later geologists, 

 Systeme Devonien, or Periode Devonienne, Beudant, D'Orbigny, Lapparent. Devonische 

 Formation, of the Germans. Devouic, International Congress of Geologists. 



As the era of the Upper Silurian passed quietly into that of the Devonian, 

 no mountain range marks the interval between them, and no abrupt transition 

 is apparent in the rocks or in the world's fauna. The Devonian was emi- 

 nently a transition era as regards land vegetation, but the culminant time 

 of aquatic Vertebrates — Fishes. The land population was low grade, it c-om- 

 prising only Myriapods, Spiders with the related Scorpions, and Insects ; and 

 not the higher Insects, since there were no conspicuous flowers over the land. 

 Terrestrial Mollusks also may have been in existence, but evidence of this 

 has not yet been reported. Th^ Devonian seas contained, in general, similar 

 Invertebrate forms to those of the Silurian, but with proportionally fewer 

 Trilobites, a profusion of Corals and Brachiopods, along with new forms of 

 Cephalopods in the Goniatites and related species. 



NORTH AMERICAN. 

 GENERAL FEATURES OF THE CONTINENT. 



The map of North America, representing its condition at the commence- 

 ment of the Upper Silurian, gives a good general idea, so far as has been 

 learned, of the continental seas and land at the opening of the Devonian era. 

 There is the same luacertainty, or error, it may be called, with regard to the 

 emerging lands over the Western Interior and Rocky Mountain region; the 

 map fails to indicate them, because the limits of such areas have not been fully 

 ascertained. These limits will in part always remain in doubt, unless deter- 

 mined by deep borings; because absence of formations from the region of 

 outcrops about Archaean mountains is far from being proof of absence beneatli 

 the plains between the mountains, or 50 miles or so distant from the 

 mountains. It is, however, almost certain that in the Devonian era the 

 Silurian island, covering much of Missouri, extended southward and westward 

 over a large part of Arkansas and Texas, and beyond, as referred to on page 

 537. The Silurian islands of Tennessee and the Cincinnati region (C and T 

 on the map, page 536) were still islands. A marked feature of the Continental 

 seas is the half-confined Northeast Bay, of the Eastern Interior; and it has 

 special importance in this era, since a large part of the described Devonian 

 beds were deposited within it and owe to its varying conditions their charac- 

 teristics. 



