344 0. C. Marsh— Vertebrate Life in America. 
are with the Crocodilia, of which order it may be considered 
the oldest known representative. In the same strata in which 
the Belodonts occur, remains of Dinosaurs are found, and it is 
a most interesting fact that these highest of reptiles should make 
their appearance, even in a generalized form, at this stage of 
the earth’s history. The Dinosaurs, although true reptiles in 
all their more important characters, show certain well marked 
ri 
enormous development both in variety of forms and in size. - 
Although comparatively few of .their bones have as yet 
been discovered in the rocks of this country, they have left 
unmistakable evidence of their presence in the foot-prints and 
other impressions upon the shores of the waters which they 
frequented. The Triassic sandstone of the Connecticut Valley 
has long been famous for its fossil foot-prints, especially the 
so-called ‘bird-tracks,” which are generally supposed to have 
been made by birds, the tracks of which many of them closely 
resemble. A careful investigation, spe: ne nearly all the 
. Specimens yet discovered, has convinced me that there is not a 
particle of evidence that any of these fossil. ‘iipreekions were 
made by birds. Most of these three-toed tracks were certainly 
detected the impressions of these anterior limbs in connection 
with the osterior foot-prints of nearly all of the supposed 
“bird-tracks” described, and have little doubt that they will 
eventually me found with all. These double impressions are 
precisely the kind which Dinosaurian reptiles would make, 
and as the only characteristic bones yet found in the same 
rocks belong to animals of this group, it is but fair to attribute 
all these foot-prints to Dinosaurs, even where no impressions 
of fore-feet have been detected, until some idler appears 
that they were made by Bi rds. I have no doubt that 
ae Boge at this time, although at paesent the proof is 
The pritieipal genera of Triassic Reptiles known from osseo 
remains in this country are, Amphisaurus (Megat) 
from the Connecticut Valley, Bathygnathus, — Prince E 
ward’s Island, Belodon and Coiisiearsh Other generic names 
a 
A 
Reptiles have been found in undoubted Jurassic rocks of 
America, but they are not sufficiently well determined to be 
