352 0. C. Marsh— Vertebrate Life in America. 
that they are an aberrant type of Reptiles, totally off the line 
through which the Birds were developed. The announcement 
made not long since in Europe, and accepted by some American 
authors, that the Piarsitagiis) ‘in consequence of certain points 
_in their structure, were essentially Birds, is directly disproved 
by American So far more perfect than those on which 
the conclusion was base 
t is now generally nilmitted by biologists who have made 
a study of the vertebrates, that Birds have come down to us 
through the Dinosaurs, and the close affinity of the Jatter 
with recent Struthious Birds will hardly be questioned. The 
case amounts almost to a set aap ag if we compare, with 
Dinosaurs, their contemporaries, the Mesozoic Birds. The 
classes of Birds and Reptiles, as now living, are separated by a 
gulf so profound that a few years since it was cited -by the 
opponents of evolution as the most important break in the 
animal — and one whi - that doctrine could not bridge 
over. Since then, as Huxley has clearly shown, this gap 
has been vatially filled by the discovery of bird-like Reptiles 
and reptilian Birds. Compsognathus and ani yiteaed of the 
Old World, and Ichthyornis and Hesperornis of the New, are 
the stepping stones by which the evolutionist of to-day leads 
the doubting ectaes across the shallow remnant of the gulf, 
once thought impassable. 
It remains now to consider the highest group of the Animal 
Kingdom, the class Mammalia, which includes Man. Of the 
existence of this class before the Trias we have no evidence, 
Marsupials, she lowest Mancosliae group hich we ey in 
to the insect- are Myrmecobius, now egies in Australia. 
ura of Hurope has ‘segs other sumnilar 
few years have brought to light i in the Eocene. 
