BaU of the Comanche Series. 11 



(iutirely tlistiiict from each other in paleoatoh:)gic cliaracters, and 

 tliat it could he approi)riately madcv^nto two divi.sions. For 

 the u})per of these, which is composed of the Cai)rinahmestoue 

 and the " Comanche Peak Group " of Shumard in part, the 

 na.me Fredericks! nirg was retained, and to the lower the name 

 Trinity Division was given, thus dividing the Comanche Series, 

 more in accord with its natural grouping, into three great divis- 

 ions, instead of two, as originally pro2:)osed. 



Since the puhlication of his Arkansas report''^ the writer has 

 devoted several years to the study of the Trinity Division in 

 Texas and Indian Territory, and has more fully differentiated 

 its heds from those of the overlaying Fredericksburg Division, 

 and, furthermore, ascertained that it constitutes a paleontologic 

 and stratigraphic division of the utmost importance in the inter- 

 })retation of the North American Cretaceous. 



In the same 'report upon the Arkansas Cretaceous a prelim- 

 inary description of the Trinity Division was made, separating 

 it into a lower or arenaceous terrane, and an upper or calcareous 

 terrane, for which, in a final pa})ert upon the stratigraphic suIj- 

 divisions of the Comanclie Series, read before the Geological 

 Society of America at its Washington meeting,. December, 1890, 

 the names of the Trinity sands and Glen Rose beds Avere re- 

 si)ectively proposed and the following general arrangement of 

 tlie series given : 



C. The Washita or Indian Territory Division. 

 10. The Denison )jeds. 



9. The Fort Worth limestone. 



8. The Duck Creek chalk. 



7. The Kiamitia clays or Schlue aback la beds. 

 B. The Fredericksburg or Comanche Peak Division. 



6. The Caprhia and Goodland limestone. 



5. The Comanche Peak chalk. 



4. The Gryplnca rock and W^ihiut clays. 



3. The Paluxy sands. 

 A. The Trinity Division. 



2. The Glen Rose, or alternating, beds. 



1. The Trinity, or luisal, sands. 



- - ^ 



* The Neozoic Geology of Southwestern Arkansas, vol. n of tlie Annual 

 Report, Geological Survey of Arkansas, 1888. 

 t Loc. cit. 



