(Sh) 
PHYLOGENY OF THE PALZOGNATHA AND NEOGNATH#, 23 
Tue Pecrorat Lui. 
The pectoral limb is in all the flightless Palwognathe a very degenerate structure. 
Perhaps that of Rhea should be regarded as the least degenerate. 
In the Rhea the length of the extended ante-brachium and manus is only very 
slightly greater than that of the brachium. The length of the manus is greater than 
the ante-brachium. The length of the pollex with its claw is very nearly as great as 
the 11. metacarpal. In a nestling Rhea I find on the 1. digit a vestige of a claw; a 
similar vestige has been already detected by Wray in the Ostrich. The ulnare 
possesses the typical Neognathine form—in Struthio this is a mere nodule. The Ist 
phalanx of the second digit is broad and flat, the 2nd phalanx is pointed. 
The ante-brachium is about one-third shorter than the brachium, The post-axial 
border of the ulna from the olecranon outwards for some considerable distance is 
greatly compressed. The superficial appearance of the forearm resembles that of 
many long-winged Weognathe. 
In the humerus the pectoral crest is obsolete, as also is the crista inferior. 
is no subtrochanteric fossa, and the fossa for the brachialis internus is only faintly- 
indicated. 
In Struthio the length of the extended ante-brachium and manus is about one-third 
less than the length of the humerus, and falls far short of that of Rhea, being but a 
little more than two-thirds as long as the brachium. 
In Struthio the manus is longer than the forearm, in Rhea the reverse is the case. 
In Rhea the forearm is about two-thirds and in Struthio about one-third the length of 
the humerus. The distal carpal mass only just reaches the base of the 1st metacarpal ; 
in Rhea it extends pre-axiad so as to support the whole base of the pollex. The Ist 
phalanx of the 11. digit is relatively longer in Struthio than in Rhea. The 1. metacarpal 
in Struthio is more or less rod-shaped, that of the 1. is rod-shaped and bowed. In 
Rhea the distal end of metacarpal 11. is flabellate, the 11. metacarpal is very slender, 
rod-shaped, and sigmoidally curved. 
The ulna, in Struthio, is much expanded distally by a more or less triangular out- 
growth of its pre-axial border. The olecranon is but feebly developed. The distal 
end of the radius is grooved and much expanded in the direction of its articular surface 
for the radiale. 
The pectoral crest of the humerus is more conspicuous than in Rhea, forming a long, 
low, swollen ridge. There is a wide and shallow fossa distad of the caput humeri, 
possibly representing the sulcus transversus. There is also a shallow incisura capitis. 
The crista inferior is wanting. The subtrochanteric fossa is present but shallow, but 
it receives no pneumatic apertures. The tuberculum medius is moderately well 
developed. 
The linea aspera for the triceps is raised into a long and sharp ridge, which reaches 
