132 GEORGE H. GIRTY 



the Gschelian or " Upper Carboniferous;" the Artinskian or " Permo- 

 Carboniferous" and the Permian. One school of Russian geologists 

 includes the Artinskian or Permo-Carboniferous beds in the Permian, 

 and some Americans have followed them, but this seems to be of 

 doubtful propriety. Murchison, DeVerneuil, and Keyserling mistook 

 the Artinsk sandstone for the Millstone grit and distinctly excluded it 

 from the Permian. If the faunal relations demand this extension of 

 the term Permian to the Artinsk it would be justifiable, but such 

 is not the case. At least, this appears to be the judgment of Tscherny- 

 schew, the chief of the Russian Survey, and other distinguished 

 paleontologists. At all events in this recital the term Permian is used 

 in exclusion of the Artinsk beds. 



The Productus giganteus zone seems to be represented on this 

 continent by the Baird shale of California whose fauna likewise con- 

 tains P. giganteus. 



The Moscovian, which has a facies very like our common Pennsyl- 

 vanian faunas, may be compared with the earliest Pennsylvanian of 

 Arizona and Utah, the term "Lower Carboniferous," as used by the 

 Russians, having no relation to our own Lower Carboniferous or Mis- 

 sissippian. The Gschelian is clearly related to our Hueco formation, 

 but with this zone the closeness of the analogy ceases. One is tempted 

 to place in alignment the Artinsk and Permian which succeed the 

 Gschelian in the Russian section, with the Delaware Mountain 

 formation and Capitan limestone which succeed the Hueco formation 

 in the American section, but such a correlation is neither sharply 

 contradicted nor substantially supported by the faunal evidence. 

 In fact, as exhibited in the literature, the faunas of the Artinsk and 

 Permian are much less varied and individualized than those of the 

 Guadalupian. The following suggestions are made with the diffi- 

 dence of second-hand and imperfect knowledge, but it would appear 

 that after the Gschelian stage there was in the Russian area a gradual 

 progression from marine to at least near-shore conditions. This 

 seems to be indicated by the great reduction in the marine facies, 

 especially in the brachiopod representation, so that in the Permian 

 there remains scarcely a tithe of the greatly diversified brachiopod 

 fauna of the Gschelian, and by the introduction of fresh-water types 

 of which not less than 60 species have been recognized. Apparently 



