L58 The American Geologist. September, 1894 
will be in perfect accord with biological conceptions to regard 
the peculiarities of the individuals in question as due to acci- 
dental variations in the form of the terminal chambers, and 
not as permanent characters indicating a distinct species. 
The } T oung of the Globigerina' float at the surface, but as the 
shells, with age, increase in size and thickness the animals 
sink through the water and their minute tests become mingled 
with those of other species that spend their entire life in the 
ooze at the bottom. Now Brad} T 's specimens of Globigerina 
digitata came from bottom dredgings. The species was never 
taken with the tow-net at the surface. It is probable that in 
each case the abnormal chambers were added after the organ- 
ism came to final rest amid the bottom ooze; and it is at least 
possible that the abnormality noticed may be due to the fact 
that amid this ooze the restrictions to normal growth are very 
much greater than those affecting the animals when floating 
freely near the surface. We have seen in the deformed and 
otherwise abnormal textularians that the simple protoplasm 
making up the bodies of Foraminifera responds to changes of 
environment in such a way as profoundly to affect the form 
and proportions of the shell; and it is quite possible that, in 
the crowded conditions existing upon the sea bottom, some 
individuals were so unfavorably situated as seriously to inter- 
fere with normal, symmetrical growth. It is an interesting 
fact that the deformed specimens of Globigerina are associa- 
ted with the vigorous symmetrical types of Textularia at 
Saint Helena. Nearer the shore, as indicated by the material 
laid down at Sioux City, Hawarden, Auburn, and other points 
east of the Iowa boundary, the Globigerina? flourished in 
greater profusion than farther west, and evidence of distor- 
tion, or any interference with normal growth, among the 
multitudes of vigorous looking individuals that crowd the 
strata in this marginal part of the Niobrara basin, are ex- 
tremely rare. 
While Textularia and Globigerina are the predominent 
types in the region under consideration, there are other genera 
that show similar peculiarities of distribution. For example, 
a very beautiful species of Truncatulina, or probably Anoma- 
lina, is somewhat common at certain levels in the exposures 
at Saint Helena and Yankton, but there is not even a trace of 
