O. C. Marsh— Vertebrate Tnfe in America. 849 
nounced by professional: explorers barren of vertebrate fossils, 
should teach caution to those who decline to accept the imper- 
fection of our knowledge to- rsh as a fair plea for the supposed 
absence of intermediate for 
n the marine Oretadeous rn of the West, be? a single 
Ditibdaur (Hadrosaurus agilis), has been found, but in e higher 
resh-water beds, which mark the close of this Dacnesols their 
Hadrosaurus and Dryptosaurus were foun n Cretaceous 
fresh-water deposits on the coast of Brazil, remains of this order 
occur, but the specimens hitherto discovered are not 
characteristic for accurate determination. This is unfortunately 
true of many Dinosaurian fossils from North America, but the 
great number of these Reptiles which lived here during the 
Cretaceous Period promises many future discoveries, and sub- 
stantial additions to our.present knowledge o 
e first appearance of Birds in America, according to our 
Leow i knowledge, was during the Cretaceous Period, although 
any announcements have been made of their existence in 
preceding epochs. The evidence of their presence in the Trias, 
ased on footprints and other impressions, is, at present, as we 
have seen, without value; although we may confidently await 
their discovery there, if not in older formations. Archeopteryz, 
from the European Jura, the oldest bird known, and now 
fortunately represented by more than a single specimen, 
clearly indicates a much higher antiquity for the class. The 
_ earliest American forms, at present known, are the Odontornithes, 
or Birds with teeth, which have been exhumed within the last 
few years, from the Chalk of Kansas. The two genera, Hes- 
perornis and Ichthyornis, are types of distinct orders, and differ 
from each other and from Archeopteryx much more than do 
any existing birds among themselves; thus showing that Birds 
are now a closed type, and that the key to the history of the 
class must be sought for in the distant past. 
n Hesperornis, we have a large aquatic he. rhe six — 
in length, with a strange combination of The ja 
are provided with teeth, set in gro OveS ; shai wings were ru Padi. 
mentary, and useless ; while the egs were very similar to those 
of modern diving birds. This last feature was merely an adap- 
tation, as the more important characters are Struthious, showing 
that Hesperornis was essentially a carnivorous swimming Ostrich. 
Ichthyornis, a small flying bird, was stranger still, om ie fort 
were in sockets; and the vertebrae biconcave, as 
and a few Reptiles. Apatornis and other allied + forins scien 
