206 



SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1921. 



and W'iddritu/fonites. The vast majority of 

 these are old genera which became extinct 

 before the dawn of the Upper Cretaceous and 

 which give the Albian facics to the Patapsco. 

 Even as regards the: angiosperm element of the 

 Patapsco, which might be expected to show 

 more similarities to only sliglitly younger 

 formations, the following genera of the Pa- 

 tapsco are not represented in the Cheyenne: 

 Cyperacites, Plantaginopsif!, AlesinaphyUum, 

 Pnpulus, FopuIoph)/Jhrm, Nelumbites, Meni- 

 .^permites, Cflasirophyllviii, Cissites, Araliae- 

 phyUurn, Hrdcraephyllum, and Aristohchine- 

 piiylhrm. 



The angiosperms of the Cheyenne flora, 

 comprising only eleven species of six genera, 

 contain but two genera that are found in the 

 Albian {Supindopsis and Sassafras) . 



Moreover, tlie Cheyenne flora entu-ely lacks 

 those supposed Dakota sandstone species 

 which are common in the Woodbine sand of 

 Texas, the Bingen sand of Arkansas, the Tusca- 

 loosa formation of Alabama, and the Raritan, 

 Magothy, and allied formations of the Atlantic 

 coast region and which clearly show that the 

 so-called Dakota flora as it stands in the litera- 

 tm-e is not a chronologic unit and that there 



is a Dakota sandstone which is approximately 

 of the same age as these formations and which 

 I am inclined to consider of Turonian age 

 according to European standards. 



I regard the Cheyenne flora as clearly of the 

 same general facies as those of the Upper Cre- 

 taceous formations that immediately succeeded 

 the Cheyenne sandstone in time and as set 

 apart from any known Lower Cretaceous floras 

 by the absence of the characteristic Lower 

 Ci'etaceous element in part exemplified by the 

 Patapsco genera of ferns, cycads, and conifers 

 enunierated in a preceding paragraph. 



The Cheyenne flora is unquestionably older 

 than the flora of the Woodbine sand of Texas, 

 for although the latter also consists largely of 

 so-called Dakota forms there is not a single 

 species that is common to the Cheyenne and 

 Woodbine, and the "Dakota" species of the 

 Wootlbine are nearly all the common forms of 

 Coastal Plain formations of known age. I 

 have recently completed a study of the Wood- 

 bine flora,'' so that these statements are 

 authoritative. 



The range of the plants found in the Chey- 

 enne sandstone is given in the appended table 

 of distribution. 



' lierry, E. W., The floni of llu' Wooiihint- saml at Arlhiirs Hlurt, Ton : V. S. Ccol. Siirvp.v I'rof. Paper 129, pp. iriH-lsl, 11)22. 



