250 Transactions.—Zoology. 
intermediate between Tribonya and Notornis, while in others it is in advance 
of Notornis, in just the same way as the latter is in advance of Tribonys, t.e., 
deviates more from normal carinate characters. 
In the shoulder-girdle the four genera form a very interesting series: this 
is shown in fig. 6 (pl. XXI.), in which all four shoulder-girdles are reduced to 
a common length of trunk, and th id perposed upon one another, 
80 as to coincide in direction. As regards relative length of coracoid and 
scapula, Notornis is seen to intermediate between Ocydromus and Porphyrio, 
Tribonyx having the coracoid a little longer than that of Notornis, the scapula 
somewhat shorter. The same series is observable in the curvature of the 
scapula ; this is greatest in Porphyrio, next comes Tribonyx, then Notornis, 
and finally Ocydromus with a scapula nearly straight save at its distal end. 
A similar gradation is seen in a more important point, namely, in the 
angle enclosed between the adjacent portions of the coracoid and scapula. 
As was first pointed out by Professors Huxley and Newton*, one of the 
most marked features of the Carinata is the fact that the coraco-scapular 
angle never approaches 180° as in Ratite, and is usually less than 90° ; 
only exceptions mentioned by either author being Didus and Ocydromus, in 
which the angle is slightly over 90°. This, then, is another morpho- 
logical character which has a definite relation to the power of flight, 
the coraco-scapular angle, like the transverse sternal angle, being found, 
speaking generally, to increase pari passu with diminution of that power. 
It would, however, be a mistake to suppose that there is anything 
like a constant relation between flightlessness and increase of the coraco- 
scapular angle. I find, for instance, that it is less in Tetrao than in Vultur, 
and that of the two skeletons of Stringops in the University Museum, one 
has the angle less than 90° on both sides, while in the other the angle on 
the left side is just over a right angle, that on the right being the same as 
in the other skeleton: so that the angle has undergone little or no inerease 
in a bird in which the carina sterni is practically obsolete, and the fureula 
rudimentary. But the strangest exception to the rule that the coraco- 
seapular angle in the Carinate is less than 90°, is furnished by that parago® 
of flying birds, the albatross, in which the angle is fully 100°; the same, 
though to a less degree, is the case in the Nelly (Ossifraga).+ Thus Dio- 
medea and Ossifraga must be added to the above list of exceptions, as well as 
Siringops (?), Onemiornis, Aptornis, Tribonyz, and Notornis. As a very general 
of this angle by Huxley and Newton. Of course if the general direction of the scapula 
be taken, the angle will be greatly dimini the 
i 
ie ee bien af ot 32 a ae a wis ee 
= 
pte, ae | 2 thn had. 
