in birds the forward toes are only three. There is a 
difference also in the number and arrangement of the 
articulations. . 
The track in our possession is twenty inches long 
by thirteen and a half inches broad. The rock in 
which it is imbedded is a dark-colored sandstone. 
President Hitchcock has a slab showing a regular 
series of tracks of this animal; the distance between 
the steps being about three feet, and the tracks equi- 
distant and alternate, which would not be the case 
if the animal had been quadrupedal. In a quadruped, 
the horse for example, the hind feet are set down near 
the fore feet, and sometimes even strike them. Hence 
it must be inferred that the track in question was 
that of a biped, or of a quadruped which did not use 
its fore feet in progression, like a kangaroo. We 
naturally ask, What kind of biped could this have 
been? Evidently not a man, the size of the foot being 
too large to admit such a supposition; nor could it 
have been a bird, the number of toes and their direc- 
tion not admitting this hypothesis. 
Tetradactylous birds, or those which have four 
toes, have only three of them directed forwards, and 
the fourth backwards, generally. There are, however, 
exceptions; some birds have four toes directed for- 
wards: this is the fact with the Hirundo Cypselus 
5 
