134 GEORGE H. GIRTY 



opinion is based upon the striking differences existing between the 

 Guadalupian and any eastern fauna, upon the much closer resem- 

 blance of the eastern faunas with the Hueconian fauna, and upon the 

 important differences between the latter and the Guadalupian. How- 

 ever, as so little is known of the character and potency of the environ- 

 mental conditions under which these faunas existed, there is a possi- 

 bility which I do not wish to deny that the relations noted may ha\-e 

 to be ascribed to the environment element, rather than to the time 

 element. 



Provisionally I am regarding the Guadalupian as younger than 

 any known faunas of the eastern region, thus interpreting the faunal 

 differences of the Hueconian when compared with the Pennsylvanian 

 and Permian of the East, as due to environment rather than to time. 

 There is some evidence, however, that the Hueco formation should be 

 considered younger than the so-called Permian of the Kansas section 

 instead of equivalent to it. Mr. Beede has recently described several 

 occurrences of a fauna which I should perhaps have mentioned as 

 representing one of the interesting and important differentiations 

 found among the faunas of the Upper Carboniferous of the East. 

 They were obtained from the red beds of Oklahoma and the horizon 

 is known to be considerably above the highest occurrences of inverte- 

 brate fossils in Kansas. This fauna appears to me to present more 

 important differences from the Kansas Permian than exist between 

 the latter and the underlying beds referred to the Pennsylvanian, 

 Accordingly, if any of the faunas of the eastern section are to be classed 

 as Permian it would appear to me more appropriate that the dividing 

 line should pass above rather than below the Kansas Permian. 

 When compared with the western faunas, that described by Mr. Beede 

 is far from being identical either with the Guadalupian or with any 

 facies of the Hueconian, but of the two its affinities appear to be decid- 

 edly with the latter. If this evidence is to be relied on, even Mr. 

 Beede's fauna is older than the Guadalupian and if the latter is equiva- 

 lent to the Permian, older than the Permian. 



Another fact which might be brought forward to support the con 

 tention that even the Hueconian is younger than the Kansas Permian 

 is the important unconformity which preceded Hueco sedimentation 

 and was accompanied by a corresponding change in the subsequent 



