396 THE POPULAR SCIENCE MONTHLY 



the Lower Carboniferous epoch another migration from western Europe 

 to the Mississippi basin took place; this was in the zone of Goniatites 

 striatus, which, as was the case with the preceding zone, did not extend 

 beyond the Mississippian Sea. At this time in the western part of North 

 America, the Great Basin Sea was connected with northern Asia, and 

 through that region with Europe. The Pacific region lacks the fauna 

 of Goniatites striatus, but has, instead, that of Productus giganteus. 

 Here, for the first time, we see a sharp differentiation into Mediterranean 

 and Pacific types of faunas, separated by the land barrier of the Eocky 

 Mountain area. 



In the age of the Coal Measures we find further evidence of con- 

 tinued invasion of the Mississippian Sea by immigrants from the 

 western European Tethys, in the faunal zone of Gastrioceras Listen. 

 This gi'oup was common in the shallow epicontinental expansion of the 

 old Mediterranean Sea, and reached America along the shores of the 

 Poseidon Ocean, the Paleozoic ancestor of the modern Atlantic, and into 

 the Mississippian basin through the Gulf of Mexico, up into Arkansas, 

 Texas, Oklahoma, Missouri, Kansas, Illinois, etc. But the western sea 

 of the Great Basin was dominated by a fauna from the boreal waters, 

 which came down through the Bering portal, along the old shore line of 

 northwestern America. The Mediterranean fauna extended eastward 

 through the Tethys to Sumatra, and up into the Ural Mountains, show- 

 ing that the Iberian, the Bokharan, and the Asia Minor portals were 

 all open. The Malaysian portal was apparently closed, and the Mada- 

 gascar geosyncline as yet shows no evidence of its existence. 



The Artinsk, or Permo-Carboniferous transition, fauna has approxi- 

 mately the same regional distribution as that of the zone of Gastrioceras 

 Listeri, except that it reached further northward, to Nova Zembla. 

 But while the Carboniferous cephalopod fauna may be considered as 

 Mediterranean in origin, the Artinsk fauna probably came from further 

 east; its real home seems to have been on the border between Asia and 

 Europe, for there it is most abundantly developed, and bears the closest 

 resemblance to its predecessors. 



At this time the northern Asiatic-Pacific fauna had a different 

 character, but is as yet little known. In America it is known in Cali- 

 fornia, and in the southern embayment that stretched from the Pacific 

 to western Texas. It is called the Guadalupian fauna, from Guadalupe 

 Mountains in Texas, where it was first described. In Texas these two 

 faunas, the Artinsk and the Guadalupian, come within a few hundred 

 miles of each other. The east and the west, the Atlantic and the Pacific, 

 were separated then, as they were during most of the Carboniferous. 



On the west, the Guadalupian or Pacific fauna, penetrated the Great 

 Basin Sea, but did not extend far inland on the continent, the high 

 lands of Utah and Idaho still separating it from the Cordilleran exten- 

 sion of the Mississippi sea. 



