692 THOMAS CHROWDER CHAMBERLIN 
borders, by great land extension, but often, perhaps dominantly, by 
diversity of land surface and by liability to climatic severities and 
diversification. Areally, land life is favored, but it is hampered by 
the climatic and topographic diversities, and these may prove graver 
obstacles to migration and intermingling than even the tongues of 
sea that previously traversed the land surface. Correlation by 
glaciation in these stages is likely to prove a valuable adjunct, but we 
must first test our criterion, for we are not as yet quite sure that 
contemporaneity of glaciation is inferred on reliable grounds. The 
shallow-water life of the diastrophic stages is driven into narrow 
border tracts and into local embayments, and is thus forced into 
special adaptations and into narrowly provincial aspects. 
(4) The early stages of quiescence and of base-leveling, with 
advancing seas, are peculiarly fruitful in biological criteria, for they 
are marked by re-expansions of the narrowly provincial shallow- 
water faunas of the previous stages. The progressive development 
of these provincial faunas and their successive unions with the faunas 
of neighboring provinces, as these come to coalesce by means of 
the progressive sea-advances, form one of the most fascinating 
chapters in life evolution, and give some of the most delicate of criteria 
for correlation. 
This rough outline is quite too meager duly to set forth the criteria 
of correlation connected with the stages of general diastrophism. It 
rather suggests them than sets them forth. 
It remains to consider the precedence among themselves of the 
three factors, diastrophism, deposition, and life development. 
We are accustomed to look to the life record as our chief means 
of correlation. Its very high utility is quite beyond discussion. 
Thoughtful students, however, recognize that the paleontological 
record is based, in an essential way, on stratigraphy and that it is 
corrected and authenticated by the precise place the life is found to 
occupy in the stratigraphical succession. Stratigraphy and paleon- 
tology thus go hand in hand, each sanctioning the other. Dzastro- 
phism lies back of both and furnishes the conditions on which they 
depend. ‘The relationship is not reciprocal in any radical sense. 
The life does not, in any appreciable way, affect diastrophism. 
Deposition has been thought to be related to mountain-folding. 
