lievien' of Recent GeologicdJ Literaftirc. 183 
REVIEW OF RECENT GEOLOGICAL 
LITERATURE. 
Bulletins of American Paleontology, Vol. 1, No. 4. The Midtraij 
Stage. By G. D. Harris. 8vo, 156 pp., 17 plates. Ithaca, June 11, 
1896. This important monograph of the lowest stage of the southern 
Eocene and its fauna is largely based on the personal observations and 
collections of professor Harris, over almost the entire area in which the 
horizon is known to occur. The author has also made good upe of the 
results of previous workers in the same field, and has studied their type 
collections so far as they are now available. 
After a brief historical sketch of the subject, the Midway stage is 
defined and reasons are given for adopting this name rather than one of 
the nvimerous synonyms that are listed in full. The classification of 
the Eocene adopted is as follows : 
f 6. Vicksburg stage, 
5. Jackson stage, 
I 4. Claiborne stage. 
Eocene Series 3^ ^ower Claiborne stage, 
2. Lignite stage, 
j 1. Midway stage. 
The Midway is made to include the Matthew's Landing and Black 
Bluff clays of Smith and Johnson. As thus defined, it is about 200 feet 
thick, and it contains the oldest marine Eocene fauna of the Gulf 
Border region. "Lithologically the Midway beds are subject to rapid 
changes. We have seen a firm limestone grade out laterally, within a 
few yards, into an incoherent sand. What is black clay on one river is 
often represented by calcareous layers on another; but upon the whole, 
the lower beds of the stage are sandy, clayey and calcareous, while the 
upper are generally clayey." 
This horizon has been recognized by its fossils, at manj- localities, in 
a zone immediately above the uppermost Cretaceous beds extending 
from the Rio Grande, some distance above Laredo, through Texas, Ar- 
kansas, Tennessee, Mississippi and Alabama, to Fort Gaines, Georgia, 
on the Chattahooche river. As might be expected, the fauna collected 
from such a long coast line shows some variation, and this is especially 
noticeable in the Chattahooche section, where the beds are mostly cal- 
careous. Professor Harris is probably right in attributing these varia- 
tions to differences in the character of the sea bottom. Similar varia- 
tions in the sediments and life of the upper Cretaceous of the same 
region have been noticed, though in this case the calcareous elements 
are nearly absent on the Chattahooche and rapidly thicken westward in 
Alabama and Mississippi. 
The most important stratigraphic fact recorded is the discovery that 
the basal Eocene of the southern states is not conformable on the upper 
Cretaceous, but the contact gives evidence at many places that there 
was an erosion interval between them. This is shown by an irregular 
surface, by lines of pebbles, and Ijy the occurrence of rolled fragments 
