The Loess at St. Joseph. — Owen. 227 
has ever been subject to alternate periods of elevation and de- 
pression. 
An objection advanced in opposition to 'aqueous deposition 
of loess is that a current flowing at the rate of even three or 
four miles per hour would carry a large quantity of coarse ma- 
terial which the bluflfs do not contain. Although this objection 
appeals to reason it is not supported by the Missouri river. At 
St. Joseph the average normal rate is seven miles per hour, at 
the surface, yet the finest sand required for building purposes 
is taken from the channel, the coarse material having been lost 
in more shallow water. . 
In view of a reasonable interpretation of observed facts the 
next question suggested is whether the snail shells are to be 
taken as evidence of the origin of the loess or if the loess is to 
be used for testimony in throwing light on the character and 
habits of its imbedded snails. It may not be impossible that 
snails have been forced to gradual changes of habit during the 
varying conditions of centuries comparable to those of the os- 
trich since its ancestors were Cretaceous water-fowl. 
In The American Geologist for December, professor 
Shimek asserts with much positiveness that, "There is not a 
single well authenticated species of fluviatile mollusks known 
from clearly undisturbed loess in this country."' Such a state- 
ment leaves no doubt as to personal conviction, but carries no 
proof of its correctness, so it may still be asked if the loess fos- 
sils can be positively identified. 
On the subject of identification of snails Theodore Gill, sup- 
porting his conclusions by those of professor Huxley, says, 
"The same kind of shell may be common to forms that are radi- 
cally different in their organization, and there is no a priori 
reason why the modifications of the shell should be of any great- 
er value than those of any other single part of the organism. 
We should in all cases allow ourselves to be guided by the con- 
sideration of the sum-total of characteristics." And continuing, 
'Tt is thus seen that the form of the shell, and even the presence 
or absence of a shell, are of very inferior systematic signifi- 
cance, and entirely subordinate to differences in structure of the 
animal." 
If this is true we are at liberty to assume that the loess fos- 
sils trom the water-tower hill, identified for professor W'inchell 
