40 EXPLANATION OF 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 others the distance varied from four 

 to six feet ; the latter was probably the longest step of this gigantic 

 bird while running. 



Next in size to these are the 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 tlie 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 

 greater length of leg than even modern 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, tlie 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 (Pal£eothrissum) have yet 

 been found in the rock containing these footsteps, which are of the 

 highest interest to the Palaeontologist, as they establish the new fact 

 of the existence of Birds at the early epoch of the New Red 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 featliered inhabitants of the present world, and were 

 adapted for wading and running, rather than for flight. 



