74 Marsh's Monograph on the Odontornithes 
earlier form, and this fact gives us a hint as to what the more 
primitive forms must have been, and suggest the more promi- 
nent features of the ancestral type. 
“In the generalized form to which we must look back for 
the ancestral type of the class of birds, we should therefore 
expect to find the following characters: 
(1.) Teeth, in grooves. 
(2.) Vertebree biconcave, 
(3.) Metacarpal and carpal bones free. 
(4.) Sternum without a keel. 
(5.) Sacrum composed of two vertebre. 
(6.) Bones of the pelvis separate. 
7.) Tail longer than the bod 
tS Metatarsal and tarsal bones free. 
4 or more toes, directed forward. 
(10.) Feathers rudimentary or imperfect. 
ancestral line of either Dinosaurs or Pterodactyles, as feathers 
were not a character of these groups. With this exception, all 
of the characters named belong to the generalized Sauropsid, 
from which both birds and the known Dinosaurs may we 
‘have descended. An essential character in this ancestral type 
would be a free quadrate bone, since this isa universal feature n 
birds, and only partially retained in the Dinosaurs now known. 
“The Birds would appear to have branched off by a single 
stem, which gradually lost its reptilian characters as it assume 
the ornithic type, and in the existing -Ratitee we have the 
survivors of this direct line. The lineal descendants of 
would come increased power of flight, as we see in young 
birds of to-day. A greater activity would result in a more 
