THE CRETACEOUS RIM OF THE BLACK HILLS. 253 



course and opens into the Minnekahta Valley. The locality is 

 on the southeast slope, just below the top of the flat-topped 

 spur-ridge and near the abrupt descent into the cafion. From 

 this point northwest to near the crest of the divide the slope is 

 moderate and nearly uniform. 



The accompanying sketch-map (Fig. 2) showing the drain- 

 age of the region north of the south fork of the Cheyenne river, 

 the Minnekahta Valley, and part of the Red Valley, will enable 

 the reader to understand the general character of the country 

 covered by this reconnaissance. 



Fig. 2. — Sketch-map of a portion of Fall River County, South Dakota. 



A B. Section No. I. C D. Section No. II. 



1. Cycad bed. 4. Upper leaf bed. 



2. Fossil forest. 5. Lower leaf bed. 



3. Plant bed. 



At the foot of this crest on the same (southeast) side, and 

 about one and a half miles northwest of the cycad locality, occurs 

 an extensive fossil forest. The wood is all completely silicified, 

 and consists of prostrate trunks of various sizes and lengths and 

 an abundance of smaller fragments, many of which are scattered 

 about on the sloping plain a long distance below the actual hor- 

 izon at which they were petrified. At that horizon many still 

 remained apparently undisturbed, and in one place a trunk eight 

 inches in diameter was seen projecting several feet from beneath 

 the massive sandstone ledge. To the south of this point is a 



