.irPvASSIC CYCADS FROM THE I'.LACK HILLS. 205 



FIELD NOTES. 

 By (i. I\. W'iKLAMi. 



A comparison of the hods on the soutlnvest side of the Black Hills 

 willi those on the east and northeast sides shows that in the former 

 th(» beds lie nearly horizontal and are deeply cut by streams, so that 

 llie lineal' exposure of tlie Jurassic is immensely increased, lliv most 

 marked chanjje is in the diminution of the sandstone l)ed beneath the 

 main Atlantosaurus beds, or Beulali shale, if, indeed, the 25 feet of 

 yellowish sandstone here intervening between this bed and the marine 

 Jurassic may be considered equivalent to the ''Unkpapa" of the east- 

 ern hills. Antl, conversely, there is an increased thickness of the over- 

 lying l^eulah shales. Thickest on the northwestern side of the hills, 

 and absent from nearly opposite Hermosa to Minnekahta, this bed, 

 teeming at its base with the remains of huge dinosaurs, incloses the 

 Black Hills like a long-armed crescent or horseshoe. 



Most unfortunately these saurian bones are seldom well preserved 

 and the collector is always baffled by one long stretch of talus after 

 another. It will prove possible, however, in the course of time, to deter- 

 mine the extensive fauna represented, and in part its silicified fiora 

 of cycads and conifers. This being, of course, an easterly extension 

 of the Jurassic so well marked farther west, most of the forms are doubt- 

 less already known. The section is of especial interest in connection 

 with the stratigraphic relations of Cycadeoidea and Cycadella. 



Section .} milen irent of Ilulett, Crnoh Count)/, W;/o. 



Feet 

 7. Various clays or sIihIps hiuI siindstoiics containing some silicified wood, iiiul doiiljl less in tlieir lower por- 

 tions the equivalent of the Blackhawk and Minnekalita cvcad beds (overlain unconforniahlv liv the 



Fort Benton Cretaceous) 2IXJ 



6. Black sliales eoiitaiuing more or less distinct remains of dinosaurs 30 



3. Bluish shale weathering white. Contains remains of large dinosaurs, .seldom well preserved, silicified 



wood, and probably cycads 12 



4. Yellowi.sh to red shale s 



',i. Clay containing three or four thin nodular layers with remains of largo dinosaurs, and ending rather 



sharply below as light sandy or nodular material 40 



2. Sharply defined stratum of yellowish sandrock, barren, so far as observed 2o 



1. Marine Jurassic, ending above in limestone weathering whitish and containing remains of Baptanoilon 



(and Megalosaurus ? ) 200 



Total (approxiuuite ) ,5,3, 



o 



