280 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Vol. VI. 



are more or less argillaceous, and containing fragments and stems of 

 leaves. 



" 3. Coarse gray and yellow sandstone. 



"4. Chocolate-colored clay shales with fossil leaves. At the uj^per 

 part these shales are black, and below pass into — 



" 5. Whitish clay shales. 



'' These last form the base of the hill. The beds are all horizontal. 

 Scattered around are fragments of a trachyte, which probably caps the 

 beds. In one of the valleys Mr. Taggart discovered, near an old well, 

 pieces of trachyte, which, on looking at the excavation, was found to be 

 the first layer penetrated. The point of overiiow from which this ma- 

 terial came is probably to the southward, in Dr. Endlich's district. The 

 lake basin may possibly be one of a chain of lakes that extended south- 

 ward. I had thought it possible that the beds were of Pliocene age. The 

 specimens obtained from bed No. 4, of the section above, were submitted 

 to Professor Lesquereux, who informs me that they are ' Upper Ter- 

 tiary.' ' But I do not believe, as yet, that the specimens of the Green 

 Eiver group, to which your species are referable, authorize the conclu- 

 sion of Pliocene age. I rather consider it, as yet, as Ui)per Miocene. 

 The species known of our Ui^per Tertiary are as yet too few and repre- 

 sented in poor specimens for definitive conclusion. Tour specimens 

 have a Myrica, a Cassia, fragments of Salix angusta (A. Br.), a Bhus^ an 

 Ulmus, and a fragment of a Foa or Poaeites.'' 



" The shales were so soft and friable that it was rather difficult to ob- 

 tain any specimens. 



"About one mile south of Florissant, at the base of a small hill of 

 sandstone, capped with conglomerate, are 20 or 30 stumps of silicified 

 wood. This locality has been called ' Petrified Stumps ' by the people 

 in the vicinity. The specimens of wood are not particularly good." 



This basin is shown on sheet 13 of the geological atlas of Colorado 

 published by Dr. Hayden's survey, and its outlines are marked with con- 

 siderable accuracy, although upon a comparatively small scale. Tlie 

 data upon which that sheet was constructed have formed the basis of 

 the accompanying map, in which the limits of the basin are given with 

 closer accuracy and in greater detail. The poiut of greatest difference 

 is in the valley of Fish Creek, where we noticed no extended prolonga- 

 tion of the lacustrine deposits ; and as the contours of Dr. Hayden's par- 

 ties themselves seem to forbid the probable extension of the deposits in 

 this direction, we have closely limited them to what we saw. 



The ancient lake lies in the valley of the present South Fork of Twin 

 Creek, and of the ux)per half of the main stream of the same after the 

 South Fork has joined it. Following the road from South Park to Colo- 

 rado Springs, and leaving it just above Florissant Post-Ofifice,* and then 



* Florissant is merely a post-office at Castello's Eanch, which is also pro\'ided Avith 

 a store, the basis of supplies for all the inhabitants within a radius of fifteen kilome- 

 ters. One would have to look far to find in Colorado a more comfortable hostelry than 

 that to which "Judge" Castello will welcome us. 



