I. Sub-class ARCHAEORNITHES.--The three fingers and their metacarpals
remain separate, each with a claw. Well-developed remiges. Both jaws
with alveolar teeth. Amphicoelous. Caudal vertebrae more than thirteen,
without a pygostyle, but with about twelve pairs of rectrices.
_Archaeopteryx, A. lithographica, s. macroura_, two specimens from the
upper Oolite of Solenhofen, Bavaria.
II. Sub-class NEORNITHES.--Metacarpals fused. Second finger the longest.
Not more than thirteen caudal vertebrae.
I. Division RATITAE.--Terrestrial, flightless. Without sternal keel.
Quadrate bone with single proximal knob. Without pygostyle. Coracoid and
scapula fused. Compound rhamphotheca. Adult without apteria. With
copulatory organ. A collective polyphyletic or heterogeneous group,
originally cosmopolitan; with certainty existing since the Miocene.
1. Order Struthiones.--With pubic symphysis. Two toes only, third and
fourth. _Struthio_, ostrich, Pliocene of Samos and of north-west
India, now Africa and Arabia.
2. Order Rheae.--With long ischiadic symphysis. Three toes.
_Mesembriornis_, Miocene or Pliocene of Argentina. Rhea, South
America.
3. Order Casuarii.--Three toes. Aftershaft as long as the other half.
_Casuarius_ and _Dromaeus_, Australian. _Hypselornis_, Pliocene of
Sivalik Hills.
4. Order Apteryges.--Four toes. Bill long and slender. _Apteryx_, New
Zealand.
5. Order Dinornithes.--Three or four toes. Bill short. Anterior limbs
extremely reduced. _Dinornis_, numerous species, recently extinct, New
Zealand.