78 The American Geologist. February, looi. 
pose characteristic biologic groups that seem to appear and 
disappear with an exactitude that expresses their identical re- 
lations to similar environments. Indeed he says :* "the pre- 
cision with which correlations may be made upon paleontologic 
evidence is determined by the knowledge possessed of the re- 
lations of the elements of organic form to geologic age, so that 
a fragment of a fossil in the hands of one who knows how to 
interpret the evidence may furnish a more correct diagnosis of 
the age of the formation than a bushel of fossils in the hands 
of one ignorant of the laws of organic life determining the 
form of the structure produced." He further in this notable 
essay alludes to the "laws of heredity and evolution," and to 
the "law of relationship of organisms to each other and to 
geologic time." And he concludes "comparisons of allied 
species in the same genus exhibits to him the rate and direc- 
tion of modification taking place in the genetic history of the 
genus, and in the plastic or variable characters he finds a sen- 
sitive indication of the stage of development attained by the 
race when the particular individual lived." 
A contribution to the genetic relationship of the inverte- 
br^e fossils of successive beds of the Tertiary was made in 
1885 by Dr. Otto Meyert who endeavored, upon the relevant 
evidence of evolutional changes, progressive in character, to 
overturn the recognized succession of the southern Tertiary 
Eocene. The succession of Claiborne (Middle Eocene), Jack- 
son (Upper Eocene), Vicksburg (Oligocene), which had been 
defined and established by Hilgard, was inferentially reversed, 
and the Vicksburg became the oldest, and the Claiborne the 
youngest stratum. In this particular instance the paleontolo- 
gist was worsted in an encounter with the less yielding and less 
supposititious data of the stratigrapher.i But Dr. Meyer's 
contribution lost none of its interest, because of a mistaken in- 
terpretation, as an index of the application of biological in- 
ferences to the questions of stratigraphy; at least Dr. Meyer's 
genealogical table was in the nature of a remonstrance against 
wholesale species making, and was a stalwart introduction of 
♦Correlation Papers, Devonian and Corbonlferous, by Hexby Shatter 
Williams; BuUetin 80 U. S. Geol. Surv., p. 263. 
fAmer. Journal Set. and Art., vols. xxlx. and xxx. ; pp. 457, 60, 421. 
tSee E. W. Hilgard, The Old Tertiary of the Southwest, Amer. Jour. 
McL, vol. XXX., p. 266. 
