908 STERNUM 
the Moas (p. 579) shews that this feature may not be of more than 
generic value. The little that is known of the skull of Gastornis 
suggests — though the suggestion depends perhaps chiefly on its 
size—that it may have had some resemblance to that of the Phororha- 
cidx, although of a more depressed form ; and the coracoid of Gast- 
ornis is as elongated and narrow as that of Phororhacos. 'That the 
Stereornithes were flightless may be considered certain, but whether 
they should rank as a Subclass with the Ratity and Carinatx, or 
should merely form an Order in one or other of these groups cannot 
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PHORORHACUS INFLATCS. Pelvis from the side and above. (After F. Ameghino.) 
as yet be determined, though the view taken by Dr. Gadow (Thier- 
reich, Vi dgel, Syst. Th. pp. 106- 114), who has placed the European 
Remiornis, Gastornis and Dasornis, together with the North-American, 
Diatryma—all of them being Eocene forms—among the Stereornithes,! 
receives support from the evident connexion between the peculiar 
and specialized Ungulates of South America and the Eocene Perisso- 
dactyl Ungulates of the Old World and North America. 
RICHARD LYDEKKER. 
STERNUM, or Breastbone, that part of the SKELETON which 
is connected with the vertebral column by the thoracic ribs and 
serves for the support of the CoRAcoIDS. Genetically it is wholly 
of costal origin. In the chick, towards the end of the first week of 
incubation (EMBRYOLOGY, p. 211), about 10 pairs of Rips are con- 
siderably elongated, so that their free ventral half extends forward 
and approaches the middle line. The distal ends of each right and 
left series soon meet and fuse, so as to form a “sternal band” of 
1 This alliance was first suggested by the writer, who, in 1889 (Nicholson and 
Lydekker, Man. Palwontol, ii. p. 1229), referred both Diatryma and Mesembriornis 
to the Gastornithide. 
