CORRELATION OF FORMATIONS 4o9 



The impression that the fossil-horizon of Red Dirt creek is the same as 

 that of the Dolores formation remains to be demonstrated by a collection 

 and study of the fauna, but the discovery of Triassic vertebrates near 

 Lander, in central Wyoming, lends strong support to the correlation sug- 

 gested by Hills. 



Triassic beds of central Wyoming. — The Triassic fauna from Wyoming 

 just referred to has been partially described by Williston in a paper pub- 

 lished since the major part of this discussion was written (44). While 

 the few forms described are new to science both generically and specific- 

 ally, their Triassic affinities are maintained by Williston. Among them 

 are representatives of the Anomodontia allied to Placerias Lucas, from the 

 Le Roux beds of Arizona, and a phytosaur related to Belodon and evi- 

 dently similar to Heterodontosuchus ganei Lucas, the common fossil of the 

 Dolores beds. 



The occurrence of the beds containing these and other fossils has not 

 been announced further than that the locality is near Lander, on the 

 Popo Agi river, which name is applied to the formation by Williston, 

 with the statement that it will be described by N. H. Brown, the discov- 

 erer, and himself. 



Other localities of Triassic vertebrate remains are known in southern 

 Wyoming, although not yet described, and it appears to the writer not 

 improbable that by systematic work the continuity of a Triassic fossil- 

 bearing formation may be established from Wyoming southward to the 

 outcrops noted by Hills adjacent to Grand river. It is possible, of course* 

 that the post-Triassic erosion may have removed the Triassic beds over 

 considerable areas, as seems to be indicated by the Hayden map. 



Permian Red beds of the Laramie basin. — Turning now to the lower part 

 of the Red beds, evidence has recently been presented by the late W. C. 

 Knight (24a) showing that in the Laramie basin of southern Wyoming 

 the Triassic strata of Hayden and King should be referred in part at least 

 to the Carboniferous system and probably to the Permian series. Knight 

 gives a section of 1,578 feet of Red beds which rest on granite. A little 

 below the middle of this section a fossiliferous sandstone was found, the 

 fauna resembling " to a marked degree the fossils of the Kansas and 

 Nebraska Permian. 1 ' Only one thin limestone was noted in the section, 

 but Knight made the significant observation " that the strata of the lower 

 portion of the Red beds are identical with the strata of limestones to the 

 northward, the difference in the lithological characteristics being due to 

 the varied physical conditions during sedimentation." 



These limestones also contain in their upper portion a fauna resem- 

 bling that of the Kansas ''Permian," but 'Knight remarks that Coal 

 Measure fossils have not as yet been collected from the lower beds. 



