FLORA OF LAKOTA OF BLACK HILLS. 325 



numbered by the collectors. It shows the immense labor which yet 

 remains to be done in completing and revising the geological history 

 of the Black Hills rim. 



Section from "Bore Hole B" at Aladdin, Wyo., beginning near the base of the Atlantosaurus shales, u'hich may 



here he 100 feet thick. 



Feet. 



8. Gray sand _ . . _ _ 4,5 



7. " Black Jack " (carbonaceous or iron-stained clay and sand ) 2 



6. Brown sandstone (contains two hard and sharp ledges) _ 30 



5. Red sandstones _ _ _ _ _ 7 



4. Gray sandstones _ X22 



3. Dark shaly clay, or the coal horizon lying over the Atlantosaurus shales proper 4 



2. Green shal}' clay of the Atlantosaurus shale proper _ 67 



1. Nodular bed, also saurian-bearing Unkpapa sandstone 20 



The latest contribution to the subject now under consideration that 

 I am able to record is the elaborate paper of Mr. N. H. Darton," published 

 in 1901 and giving the results of his work in the Black Hills, mainly in 

 the seasons of 1898 and 1899. The hydrographic part of this paper 

 does not, of course, concern us here, and in his geological work Mr. Darton 

 has paid little attention to paleontology, especially to paleobotany, but 

 there are certain facts relating to fossil plants that he could not wholly 

 ignore. He has not, however, contributed anything new to this subject, 

 unless it be a sketch (pi. Ixxvi, facing p. 526) of the large silicified trunk 

 and stump described on page 552 of my paper on the Black Hills." If the 

 sketch is correct it would seem that a number of large segments from the 

 middle portion have been removed since I was there. Mr. Darton has 

 reproduced my plate Ixxx (op. cit.) illustrating the most beautiful of the 

 cj^cadean trunks, Cycadeoidea pulcherrima, which forms his plate Ixxvii, 

 but he does not give the name of the species or state to what genus these 

 trunks belong. 



The only interest, therefore, that this paper possesses for the paleo- 

 botanist is its geological part. It is here that for the first time he describes 

 the Lakota formation, named by him in 1899 (see p. 315). This 

 formation is treated on pages 526-529, but out of the Lower Cretaceous 

 included in my sections, and extending from the Jurassic to the Dakota, 

 he makes three formations, viz, the Lakota, the Minnewaste limestone, 



a Preliminary description of the geology and water resources of the southern half of the Black Hills and 

 adjoining regions in South Dakota and Wyoming, by Nelson Horatio Darton: Twenty-first Ann. Rept. U. S. 

 Geol. Surv., Pt. IV, 1901, pp. 489-599, pi. Iviii-cxii. 



i Nineteenth Ann. Rep. U. S. Geol. Surv., Pt. II, 1899. 



