2 54 THE JOURNAL OF GEOLOGY. 



saddle, beyond which the crest of the divide is lower, and here 

 the forest is seen to the best advantage. The most prominent 

 object is an immense trunk, thirty inches in diameter and twenty 

 feet long, lying where it fell at no very remote date, having 

 broken from its roots at the surface of the ground, leaving por- 

 tions of the stump still exposed. The entire root could proba- 

 bly be exhumed. About the present trunk the lines of splinters 

 and smaller fragments clearly indicate the character of its 

 branches and show that these branches remained attached at the 

 time it fell. A considerable amount of silicified wood occurs 

 also at the same locality as the cycads, obviously preserved by 

 the same influences that preserved the latter. The slope from 

 the fossil forest to the cycad bed is about the same as the dip of 

 the strata. It is therefore probable that both occur approxi- 

 mately at the same horizon. The whole of this region, includ- 

 ing the entire crest of the divide and extending to the bottom of 

 the canon below the cycad bed and far to the southeast, consists 

 of the series of sandstones that have been treated in the Black 

 Hills report as the "Dakota Group." 



The great improbability that the cycads could have lived in 

 the Dakota period, or Upper Cretaceous, led us to undertake an 

 investigation of these rocks with a view to the possible discovery 

 of additional evidence of their age. No other fossil remains 

 than the wood and cycad trunks could be found in the immedi- 

 ate vicinity or anywhere on the outer slope of the Cretaceous 

 rim. The crest above the fossil forest consists of harder sand- 

 stones, chiefly massive, which may be traced far around the 

 Hills, and which form the upper part of the abrupt escarpment 

 above the soft Jurassic and Red Beds. Passing over this to the 

 northwest we descended into the first lateral canon entering Red 

 Valley from the northeast. The Jurassic is passed through and 

 the Red Beds fairly entered in the descent. Fifty to seventy- 

 five feet above the Jurassic contact and 175 to 200 feet below 

 the summit of the crest, argillaceous shales with some carbon- 

 aceous matter occur interstratified with the sandstones, and at 

 this level, partly in the shales and partly in the rocks, a few fos- 



