RECAPITULATION OF PALEOZOIC PORMATIONS. 161 



In the Tenmile folio, however, Emmons, while recognizing the data upon which 

 Spurr proceeded, in the lack of direct evidence as to the age of these beds, still 

 retains them in the Silurian, infiuenced to a considerable extent by the unconformity 

 which intervenes between it and the overljdng Leadville limestone. Although Spurr 

 found Devonian fishes in the Parting quartzite at Aspen, it should be borne in mind 

 that similar fish remains of Devonian types occur in the Harding sandstone, whose 

 Ordovician age seems to be secure, and in the calcareous division of the Yule 

 limestone in the Crested Butte quadrangle, of whose Ordovician age there is also 

 little doubt. In view of these facts the force of this evidence is largely destroj^ed. 

 Considering that the onlj' known Paleozoic horizon in Colorado distinguished for its 

 fish remains is in the Ordovician, that the Parting quartzite is separated from the 

 Leadville limestone, at Leadville at least, bj' an erosional unconformitv, and that 

 the lower portion of the Leadville limestone contains over large areas a Devonian 

 fauna, it seems to me that the evidence preponderates in favor of the Ordovician 

 rather than the Devonian age of the Parting quartzite. This, however, is onh' 

 another of the departments in which further and thorough research is necessary 

 before a satisfactory conclusion can be reached. If the Parting quartzite should 

 prove to be Ordovician, it would bring out a certain correspondence between 

 the early Paleozoics of the Front Range and those of central Colorado, for the 

 Manitou limestone and Harding sandstone of the one show a certain resemblance to 

 the Yule limestone and Parting quartzite of the other, which, while not extremelj^ 

 close, certainly gives the two sections more uniformitj^ than if the Parting quartzite 

 were Devonian. Both the Parting quartzite and the Harding sandstone are siliceous, 

 they are variegated in color, have about the same .thickness, and are characterized 

 b}- containing fish remains. It is true, however, that the abundant Trenton fauna of 

 the Harding is not yet known in the Parting quartzites, and that the Yule limestone 

 in the Crested Butte quadrangle also contains fish remains, while none have been 

 noted from its possible equivalent, the Manitou limestone. 



DEVONIAN. 



There is an undoubted Devonian horizon in Colorado. The fauna was originally 

 discovei-ed in the San Juan region and it has since been recognized at widely sep- 

 arated points through the State. These fossils were first listed and described bj' 

 Meek", who identified the horizon as Devonian. Later, C. A. White* found some 

 reason, which was never stated, for regarding it as Carboniferous. More recently 

 extensive collections were made in the San Juan region bj' Whitman Cross and A. C. 

 Spencer, who procured a large fauna, which I described in 1900.'' The latter fauna is 



iiU. S. Geol. Geog. Surv. Terr., Bull,, vol. I, id ser., No. I, p. 46, 1875, see also 0. S. Geol. Geog. Surv Terr . [Eighth] 

 Ann. Rept. for 1874, 1876, pp. 212-214. 



'iCont. Invert, Pal., No. 6, p. 133, 1880 (extracted from the Twelfth Ann. Rept. of the Hayden .survej- for 1878). 

 cXJ. S. Geol. Surv., Twentieth Ann. Rept., pt, 2. pp. 25-81. 



U36dt— No. 16—03 11 



