26 NEORNITHES RATITAE CHAP. 
descendants of the Archaeornithes, as each may be a separate 
offshoot from the same parent stem. All we can safely assert 1s, 
that the former were in existence about the end of the Jurassic 
times, that teeth were still retained in some cases during the 
Cretaceous Epoch, and that not only normal forms, but also flight- 
less forms without keel or pygostyle,’ had arisen by that date. 
(A) The Ratitae are commonly characterised as Birds with no 
keel to the sternum; but this will not hold as a definition, since 
Hesperornis has also that peculiarity, while such genera as Didus, 
Stringops, Cnemiornis, and Notornis are nearly in the same con- 
dition. It is no one point, therefore, but the sum of many, which 
enables us to draw so clear a line of demarcation between this 
primitive group and the remainder of existing forms; neverthe- 
less it is convenient to preserve the name unaltered, as it is well 
understood to what members of the class it is more especially 
meant to apply. The rhamphotheca, or horny sheath of the bill, 
instead of being simple, is composed of several more or less separate 
pieces, as in the Procellaridae, Tinamidae, and Steganopodes ; the 
quadrate bone, by means of which the lower jaw is articulated to 
the skull, in place of two proximal knobs has only one, as in 
Hesperornis, Ichthyornis, and the Tinamidae; the coracoid and 
scapula are fused together, and meet at an obtuse, as opposed 
to an acute or right, angle; and the last six or seven caudal 
vertebrae do not coalesce into a pygostyle, or upright triangular 
expansion to carry the rectrices, a state of things found else- 
where in Hesperornis and the Tinamidae.” The reduced wings 
preclude flight; the tail is functionless, as in the Podicipedidae 
and Tinamidae; the tongue is very small; the oil gland is 
absent ; the penis is large and erectile, beiwrg comparable to that of 
the Anseriformes ; while in the adult the feathers are evenly dis- 
tributed over the whole surface, as in the Spheniscidae and Pala- 
medeidae, no down being present. Claws are found on the pollex 
and index in Struthio and Rhea, or occasionally on the third digit ; 
in Casuarius, Dromaeus, and Apteryx they occur only on the index. 
tatite Birds proper are comprised in six groups, STRUTHIONES 
or Ostriches, RHEAE or Nandus, MEGISTANES or Cassowaries and 
Emeus, APTERYGES or Kiwis, DINORNITHES or Moas, and AEPYOR- 
NITHES or Rocs. 
‘ H. Gadow, Bronn’s; Thier-Reich, Aves, Syst. Theil. 1893, p. 90. 
* A pygostyle is occasionally found in Struthio and Apteryz. 
