REVIEWS 815 
so-called Dakota formation of the Black Hills belongs to the Lower 
Cretaceous series. This conclusion, together with the observations 
which led up to it, he published in the JouRNAL oF GEOLOGy in the fol- 
lowing year. Since that time the work of investigation has been 
greatly extended through the efforts of Professor Ward and_ his 
co-laborers, with the result that his former conclusion is now fully 
substantiated. 
New fossil localities were found, and many new species were col- 
lected. Of the cycads, one hundred and twenty-six trunks and frag- 
ments were examined. These were collected from two general although 
widely separated areas. The collection contains twenty-one species, 
all of which are new to science. Fossil forests are mentioned as occur- 
ring at the same horizon. 
Professor Jenney makes a report on the Hay Creek region, in which 
he finds: a marine Jura characterized by an abundant invertebrate 
fauna; a later Jura resting unconformably upon the former, and char- 
acterized by saurian bones and fossil wood ; above this the Lower Creta- 
ceous, which he subdivides as follows: (1) the Hay Creek formation ; 
(2) the Barrett shales ; (3) the Oak Creek beds. ‘The series is charac- 
terized by an abundant flora which contains no cycads. 
The flora of the region is described by Professor Fontaine, who 
finds a number of species common to the Potomac formation, and a 
few common to the Kootenai. This suggests a closer relation with the 
eastern flora, but Mr. Ward thinks that this may not be the actual con- 
dition, as the Kootenai flora has not been as thoroughly investigated 
as the Potomac. 
A few outcrops of the ‘‘Atlantasaurus beds ”’ are reported as occur- 
ring on the eastern flank of the Black Hills. These consist of clays rep- 
resenting a thickness of about fifty feet and containing bones of 
saurians. The beds are thought to have been laid down in the depres- 
sions of the eroded surface of the marine Jura. W. N. Locan. 
The Geology and Physical Geography of Jamaica: Study of a Type of 
Antillean Development. By Rosert T. Hix. Bulletin of 
the Museum of Comparative Zodlogy at Harvard College, 
Vol XX X1V5 1800. .pp.256,.41 plates. 
The general scope of this volume, which is an important addition 
to the work which the author has heretofore done on Antillean geology, 
