870 The American Naturalist. [October. 
To the Odontotorm^ one order only is referred. It is thus 
characterized : 
Teeth in sockets; sternum keeled; wings well 
developed ; ischium and pubis free pos- 
teriorly ; Pteropappi. 
The family of the Ichthyornithidae is the only one known to 
belong to the Pteropappi. 
The superorder Eurhipidur^ includes all recent birds. There 
are three orders, which are defined as follows : 
Palate dromaeognathous ; pelvic elements free pos- 
teriorly ; DromcBognatha. 
Palate not dromaeognathous ; pubis free from 
ischium ; integument covered uniformly with 
feathers, which are not differentiated on the 
wings ; Impennes, 
Palate not dromaeognathous ; vertebrae mostly 
saddle-shaped; ilia and ischia anchylosed 
behind ; ilia anchylosed to sacrum ; mandi- 
bular rami coossified at symphysis ; feathers 
with definite local distribution, those of the 
fore limb much deferentiated ; Euornithes. 
The DroMvEGGNath^ include the following suborders : 
Sternum without keel ; clavicles ; wings rudimental ; Struthiones. 
Sternum without keel ; no clavicles ; wings rudimental ; Apteryges. 
Sternum with keel ; clavicles ; wings rudimental ; Gastornithes. 
Sternum with keel ; clavicles ; wings functional ; Crypturi. 
The families belonging to these orders are the following : 
Struthiones; Struthionida^, Rheidae, Casuariids, Dromaeidae, 
Dinornithidae, Aepiornithidae. 
Apteryges ; Apter^^gidct. 
Gastornithes ; Gastornithida^. 
Crypturi; Crypturidae. 
To the Impennes but one suborder belongs. This is the Ptilopteri. 
Ilium not anchylosed with sacrum ; bones of wing not 
foldable on each other ; metacarpals not separated ; 
hallux directed forwards ; feathers scale-like ; ver- 
tebrae opisthocoelous ; Ptilopteri. 
