944 The American Naturalist. [October, 
I. Time correlation of the clastic rocks. 
1. Correlation by structural data. 
a. By stratigraphical data. 
4. By lithological data. 
c. By physiographical data. 
2. Correlation by paleontological data. 
a. By fossil plants, a. By marine fossils. 
or 
4. By fossil animals, b. By terrestrial fossils, 
II. General geological color schemes and other graphic conventions. 
II, Genetic classification of the Plistocene rocks. 
The consideration of the first division of the above plan was taken 
up by the presentation of a synopsis of the subject by Prof. G. K. 
Gilbert. The third part of the subject was opened by the presentation 
of two systems of glacial phenomena, one by President Chamberlin 
and the other by Mr. W. T. McGee. The discussion was as follows: 
Prof. Gaudry spoke as follows: In the Parisian basin there are two 
different horizons distinguished by different faunas, the one indicating 
a cold, the other a warm climate. It is, however, impossible to decide 
` which of these two periods was the earlier. In England the same con- 
dition of affairs is to be observed. In Germany there is but one 
Quaternary fauna, which indicates a cold climate, whilst in Italy the 
fauna of the cold period is absent. : 
Prof. H. Credner: The North German plain contains deposits 
closely related to those of the Plistocene in America. Prof. soap 
lin’s classification is admirable and wholly applicable to Germ 
Baron de Geer expressed his approbation of the aon po 
posed by Prof. Chamberlin. He had for some years been advocating 
a similar classification for Scandinavia. A few minor alterations might 
be suggested to suit Scandinavian conditions ; for instance, the marine 
deposits might be made’ a separate class; classes IV. and V. of Prof. 
Chamberlin could, perhaps, be reduced to subclasses under III., as 
the formations frequently seem to be accidental or local. He agreed 
with the distinction suggested between osars and kames,—that is, that 
the former are in the main radial and the latter peripheral with refer- 
ence to the distribution of land ice. 
Prof. T. McK. Hughes pointed out that the classification given by 
Prof. Gaudry was purely chronological, whereas that suggested 2 
Prof. Chamberlin was purely genetic. He then explained the abun 
dance of striated boulders in one part of the glacial deposits and their 
absence in another. If the supply of material (that is, of rock bosses — 



