40 EXPLANATION' OF PLATE 26 a . 



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. 26a. 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. 26b. 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 impres- 

 sions 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. 26a. 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 Jeg than even modern Grallse. 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 shallow 

 water that was subject to changes of level, and in which sediments 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 (Palseothrissum) have yet been found in the 

 rock containing these footsteps, which are of the highest interest to the 

 Palaeonthologist, as they establish the new fact of the existence of 

 Birds at the early epoch of the New Red sandstone formation ; and 

 further show that some of the most ancient forms of this class attained 

 a size, far exceeding that of the largest among the feathered inhabi- 

 tants of the present world, and were adapted for wading and running, 

 rather than for flight. 



