152 Claypoie on ''Darwin and Geology. 
33. Leptolhnn<ra . One perfect specimen of a Lepto- 
iimnara unlike any local living species was found, 
33. Physa . One young specimen was found. The 
species could not be determined. 
34. Hdlciria occulta Say. Abimdant. The fossils aver- 
iige smaller than the several thousand recent specimens taken 
near Iowa City, hut are nearly equal to the specimens from 
Eldora, Iowa. 
35. Pisidiutfi . Two perfect yalves and several frag- 
ments of others were found. The species could not be satisfac- 
torily determined. 
It will be observed that with the exception of Helicina oc- 
culta Say and Pisidiuni all of these mollusks are Pul- 
monatcs. Of this list numbers 4, 6, 11, 12, 13, and 22 are now 
extinct in this locality. Numbers i, 7, 8, 9, 10, and 20 (the 
first form) have remained unchanged. Numbers 2, 14, 16, 18, 
19, 21, and 24 are now better developed than formerly, and 
numbers 3, 5, 15, and 17 have degenerated. Numbers 14, 19, 
and 24, are placed in the list of forms which, in this locality are 
better developed than formerly, but specimens from other parts 
of the state approach our fossils very closely. The probable 
causes of these variations will be discussed in the future. 
DARWIN AND GEOLOGY. 
BY PROF. E. W. cr.AYPOLE. 
The publication of the Lijc of Charles Dariviti by his son 
has afforded a suitable opportunity to review the labors of this 
greatest of recent naturalists. Charles Darwin was not a biolo- 
gist on the model of those who limit the field of biology to the 
study of structure with the aid of the microscope and the micro- 
tome. Invaluable as are these engines of research they had 
little or no place in his laboratory. But in the wide field of ob- 
servation and experiment, not with the dead but with the living 
organism, he was a biologist of the first rank. With this de- 
partment of his work, however, we have little direct concern. 
But a man of the first rank in one department of nature is al- 
most sure to cross the limit and enter on the ground of other 
