16 The American Naturalist. [January, 
not rise from the level of the water, but is piled upon a bank 
of sand a number of feet above the river. All debris from 
the section laid bare falls a distance below the shell deposit, 
and an implement found embedded ata point in the sand 
where the shell begins is considerably above the debris from 
the section, and must, in the writer’s opinion, have occupied 
that position since the foundation of the shell-heap. 
During the investigations of the writer, which covered a 
period of upward of seven months during the years 1892--1893, 
steam motive power reducing to a minimum time devoted to 
transit, several hundred excavations were made in upward of 
eighty localities. But a small number of objects of stone were 
discovered under conditions positively identifying them as 
being contemporary with the construction of the heaps; a 
number entirely disproportionate, one would think, to the 
amount of material displaced. 
Before proceeding to a detailed account of the worked stone 
found by the writer in the shell-heaps of the St. John’s, it may 
be well to specify the nature of the conditions referred to 
above. The writer has had occasion to state in previous 
papers of this series that the shell-heaps were occupied as a 
place of residence by later Indians, and that some at least 
were cultivated by them. The maximum depth of a furrow 
in a shell-heap is eight inches, and it is probable that the rude 
implements of the Indians went no deeper. Allowing ten 
inches as a maximum deposit of surface loam since the final 
abandonment of the mound, a depth of eighteen inches is 
arrived at, lower than which it is necessary to go to insure & 
satisfactory identification as to the period to which any imple- 
ment belongs. 
: If, however, sweet oranges are growing upon the shell-heap 
it is necessary that even a greater depth be attained. -It is 
believed that the sour orange trees, so numerous upon many 
of the shell-heaps, are descended from sweet trees run wild, 
planted by later Indians from seed furnished by the Spaniards. 
Be this as it may a majority of the shell-heaps north of Lake 
Harney were until a comparatively recent date thickly covered 
with a growth of sour orange trees. It has been found in 
Florida that the most available orange trees are derived from 
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