* 
54 Two New Species of Fossil Footmarks. 
was in an incipient state, or had not begun. The resemblance is 
certainly rather striking between this sketch and that on fig. 1: 
and it leads to the suspicion that some of the tubercular impres- 
sions of the track may have been made by the metacarpal bones. 
Such I suppose to be the character of a, a, a, a, fig. 
when these were fully ossified, it is easy to. conceive that they 
might have been anchylosed into the structure in fig. 1, A 
Professor Agassiz stated a principle of comparative anatomy, in 
conversation on this subject, which is highly important, viz. that 
the structure of adult fossil animals, that lived as early as the new 
red sandstone period, corresponds more nearly with the embry- 
onic structure of existing animals than with their adult develop- 
ment. ‘Taking this principle in connection with the above draw- 
ing of the embryo-frog’s foot, we are led to the éonclusion, that 
the animal which made these huge footmarks was probably a Ba- 
trachian. 
It may seem a strong objection to such a conclusion, that the 
animal was a biped: for what an anomalous being would a biped 
frog be, with feet twenty inches long! And yet there is one ge- 
nus of living biped Batrachians, including the Siren lacertina of 
Linnzus ; and its feet have four toes in one species, and three in 
another.* ‘True, these animals have an enormously long tail drag- 
ging behind. Yet it is not improbable, that in the new red 
sandstone period, their bodies may have been more like that of a 
bird: and such must have been essentially their form in order to 
have produced the row of tracks exhibited on fig. 1. That bi- 
Saurians existed in the new red sandstone period, we know 
from the case of the Rhyncosaurus: and the Pterodactyl proba- 
bly walked for the most part upon two legs. And it is quite as 
easy to admit the existence of biped Batrachians as biped Sauri- 
ans. ‘There is also reason to suppose, that some of these animals. 
: e been somewhat intermediate in their characters, and 
have exhibited, liké the Rhyncosaurus and Pterodactyl, a struc- 
ture now found only in several classes of animals. 
Genus Orozoum, (10s, the giant Otus, and Zwor.) 
Foot tetradactylous, pachydactylous ; toes all directed forward : 
the inner one shortest ; the second longer, and the third the long- 
est; the fourth but little shorter: all making distinct tubercle- 
like phalangeal impressions, the inner toes most so. Phalangeal 
impressions on mud, three by the inner toe, four by the second, 
and three by the two outer toes. 'T'wo bones of the metacarpus, 
articulated to the phalanges of the two outer toes, make a distinct 
impression. Cushion beneath the carpus arching downward, an 
sloping upward posteriorly. Animal bipedal. 
* Cuvier, Régne Animal, Tome ii, p. 120. 
