C. R. Stauffer — The Minnesota Devonian. Ill 



one with many similarities to that found typically in the 

 Onondaga of New York and Ohio, but Hamilton and 

 Chemung species are apparently not lacking in it. This 

 relationship cannot be wholly accidental. But perhaps 

 the most significant fact about this Devonian deposit is 

 that it carries such a large percentage of species not 

 known as a part of the eastern fauna. Many of these 

 occur in the Iowa Devonian fauna especially in the upper 

 beds. But there is still a considerable residue of forms 

 most of which have not been specifically identified. It is 

 in this latter that hope lies in an attempt to trace the 

 Cedar Valley fauna, which probably has its ultimate origin 

 in the Devonian of Russia and western Europe, or some 

 region which supplied emigrant to all three of these areas. 

 About 20% of the Minnesota Devonian species occurs in 

 the fauna of the Great Basin Devonian and 30% more of it 

 may be the same as those listed by Walcott (14). In the 

 6000 feet of limestone, which make up the lower division 

 of the Devonian of the Great Basin, nearly the whole of 

 Walcott 's collection came from the lower 500 feet, thus 

 leaving more than 5000 feet of massive limestone almost 

 unexplored and a fruitful field for future research. The 

 relationship that exists between the fauna of the Cedar 

 Valley limestone of Minnesota and that of the Devon- 

 ian limestone of the Great Basin, and somewhat more 

 remotely of the middle Devonian of some of the Alaskan 

 islands, has suggested the Paleogeographic map which 

 accompanies this paper. It is in part a modification of 

 one of Professor Schuchert's Devonian maps but it con- 

 tains much for which he bears no responsibility. A map 

 of this sort can only be suggestive of the conditions as 

 they probably existed during any period or epoch. This 

 follows from the fact that there has been so much erosion 

 during subsequent time and this has probably removed all 

 traces of the older deposits over wide areas, while land 

 barriers that once existed have been likewise obliterated. 

 Such maps are therefore subject to constant revision as 

 new facts are discovered and new relationships become 

 evident. The most striking fact that comes out during 

 this study is the remoteness of the relationship between 

 the fauna of the Cedar Valley limestone of Minnesota and 

 that of the Devonian of Manitoba. 



Am. Jour. Sci.— Fifth Series, Vol. IV, No. 23.— November, 1922. 



27 



