40 
EXPLANATION OP PLATE 26“. 
The fossil tracks on this Plate are all nearly on the same 
scale: viz. one-twenty-fourth. The recent footsteps are on 
a larger scale. 
four feet from one another. In otliers the distance varied from four 
to six feet; tlie latter was probably the longest step of this gigantic 
bird while running. 
Next in size to these are tlie footsteps of another enormous bird 
(PI. 26\ Fig. 4.) having three toes of a more slender character, mea- 
suring from fifteen to sixteen inches long, exclusive of a remarkable 
appendage extending backwards from the heel eight or nine inches, 
and apparently intended, like a snow shoe, to sustain the weight of 
a heavy animal walking on a soft bottom. (See PI. 26*’. Fig. 2.) The 
impressions of this appendage resemble those of wiry feathers, or 
coarse bristles, which seem to have sunk into the mud and sand 
nearly an inch deep ; the toes had sunk much deeper, and round 
their impressions the mud was raised into a ridge several inches high, 
like that around the track of an Elephant in Clay. The length of 
the step of this Bird appears to have been sometimes six feet. On 
the other tracks the steps are shorter, and the smallest impression 
indicates a foot but one inch long, with a step of from three to five 
inches. (PI. 26\ 2. 3. 5—14.) 
In every track the length of the step increases with the size of the 
foot, and is much longer in proportion than the steps of any existing 
species of birds ; hence it is inferred that these ancient birds had a 
gTeater length of leg than even modem Grallae. The steps at four 
feet asunder probably indicate a leg of six feet long. 
In the African Ostrich, which weighs lOOlbs, and is nine feet high, 
the length of the leg is about four feet, and that of the foot ten 
inches. 
All these tracks appear to have been made on the Margin of shal- 
low water that was subject to changes of level, and in which sedi- 
ments of sand and mud were alternately deposited, and the length of 
leg, which must be inferred from the distance of the footsteps from 
each other, was well adapted for wading in such situations. No 
Traces of any Bones but those of fishes (Palmothrissum) have yet 
been found in the rock containing these footsteps, which are of the 
highest interest to the Paleontologist, as they establish the new fact 
of the existence of Birds at the early epoch of the New Bed sand- 
stone formation ; and further shew that some of the most ancient 
forms of this class attained a size, far exceeding that of the largest 
among the feathered inhabitants of the present world, and were 
adapted for wading and running, rather than for flight. 
