I903-] Gidley, Fresh-water Tertiary of Northwestern Texas. 623 



points show great variations in details of character and in the 

 relative thickness of the different strata. No. i belongs to the 

 Triassic, which apparently underlies the whole of the Staked 

 Plains. No. 2 of the section, designated by Cummins as 

 "Reddish clay," is probably of Miocene age, as will be shown 

 later. Unfortunately no characteristic fossil remains have 

 been found in this stratum to fix definitely its geological 

 position. However, it is older than the Sheridan beds, as are 

 also the strata which bound them on the north and south. 

 The Sheridan beds are unconformable with those of this older 

 formation and apparently mark the course of an ancient 

 stream which, after scooping out a channel or narrow valley in 

 the older formation, refilled it again in Pleistocene times. 



Fig. I, page 625, is a diagrammatic cross-section across Tule 

 Canon near its head. 



There is nothing in the character of the deposits to indicate 

 beds of lake formation. On the contrary, the distribution of 

 the beds, which are nowhere very wide but extend several 

 miles east to the edge of the Plains, indicates, rather, an allu- 

 vial origin. The sharp cross-bedding of sand, gravel, and clay, 

 which the writer observed at certain points in the formation, 

 and the peculiar distribution of the coarser gravels, all indicate 

 the depositions of a river or smaller stream rather than those 

 of a lake. A further indication of an alluvial derivation of 

 these beds is that the fauna represented consists wholly of 

 land forms, and some of the bones show weather checking. 

 The wind, carrying large quantities of fine sand and dust from 

 the surrounding plains, may also have played a very important 

 part in forming these deposits. 



Following is a list of species from the beds at Tule Canon, 

 as given by Cope ^ : 



TeSTUDINATA. DlPLARTHRA. 



Testudo hexagonata Cope, Equus excelsus Lcidy, 



" laticaudata Cope. " semiplicaius Cope, 



Edentata. " tau Owen, 



Mylodon ? sodalis Cope. " major Dekay,^ 



Proboscidia. Holomeniscus sulcalus Cope, 



Elephas primigenius Blum. 2 " macrocephalus Cope. 



' Rep. Geol. Surv. Texas, 1S92 (i.S()3), p. 87. 

 ^ Elephas primigenius, probably E. imperalor. 

 ' Equus maior — E. coniplicatus. 



