TIID RELATIONS OF SOME CARBONIFEROUS FAUNAS 23 



while I am tentatively placing it at the horizon of the " Per- 

 mian " of the Grand Canyon section and of the Delaware sand- 

 stone of the Guadalupe Mountains. My evidence is not con- 

 clusive, but certainly no fauna at all like that of the Capitan is 

 known in Utah underlying the " Permo-Carboniferous," while 

 the Aubrey group, which occurs beneath the " Permian " of the 

 Grand Canyon, probably represents the upper part of the Hueco 

 formation, though it may be partially equivalent to the Delaware 

 Mountain formation. 



On tlie whole, therefore, it seems to me rather more probable 

 that much if not all of the Capitan and Delaware formations is 

 younger than the Schivagerina zone. The explanations as to 

 the partial resemblance of the Capitan fauna to the Schivagerina 

 fauna called for by this hypothesis, are certainly no more diffi- 

 cult than in the opposite case. Even if these series of rocks 

 are admitted to be younger than the Schivagerina zone, how- 

 ever, it does not follow that they correspond to the true Permian, 

 rather than to a horizon not represented in the Russian section ; 

 but from the considerations set down above this would appear 

 to be the case. 



In even so cursory and incomplete a comparison of the Amer- 

 ican with the Russian faunas, one feature of the latter is too 

 striking to be entirely neglected. American paleontologists 

 have come to look upon the genus Archimedes as diagnostic of 

 our Mississippian series, and to us it comes as an almost start- 

 ling anomaly that this type is well represented in the upper 

 Carboniferous of Russia. It seems, indeed, to be especially 

 characteristic of the highest beds (the Schivagerina zone), from 

 which Tschernyschew cites 4 species, one of them our own 

 Archimedes wortheni. No trace of this genus has been ob- 

 served in any of the Trans-Pecos faunas, yet its occurrence in 

 the Upper Carboniferous of this continent is not entirely un- 

 known, since White cited Archimedes associated with an Upper 

 Carboniferous fauna from the Uinta Mountains.' Four or 5 

 years ago I also collected the genus in abundance in the Bing- 

 ham mining district, Oquirrh Mountains, Utah, associated with 

 a fauna, which is certainly not one of those characteristic of the 



iRept. Geol. Uinta Mountains, etc., 1S76, p. 80. 



