692 PROF. OWEN ON THE STERNUM OF NoTorNis. [Noy. 28, 
the process so called’, but is slightly concave : its extent equals that 
of the coracoid margin, 6, the pair of which margins, with the manu- 
brial one, divide the fore border of the sternum into three equal parts. 
The degree of transverse concavity is the same in each; but the 
coracoid ones have also a moderate excavation in the opposite direc- 
tion for their articular relations with the scapular arch. The outer 
end of each of these joint-surfaces is slightly produced (ib. d@). 
Articular cavities for the sternal ends of six hemal ribs mark the 
costal division, ¢c, c, of the outer border, which is thence continued 
backward, with a very slight sigmoid curve, to the hind end of that 
border, one third of which bounds the part of the sternum converted 
by the deep notch, f, into a “ postmarginal”’ process, g. The in- 
termediate end of the sternum, a, representing, though hardly homo- 
logous with, the “ xiphoid appendix,” in ‘‘ Anthropotomy,” is ter- 
minally truncate, not extending so far back as the ‘“ postmarginal ” 
processes: these resemble the same parts in Tribonyz in being un- 
expanded at the end, as is slightly the case in Ocydromus and 
Porphyrio. The sternal keel in Notornis (figs. 1 and 2, s s') shows 
the same shallowness asin Tribonyx, with a further reduction of the 
anterior angle (fig. 2, s'), in which Notornis resembles Ocydromus. 
The transverse convexity of the sternum, reduced as it is in that 
genus, is relatively less in Notornis : it subsides almost to flatness in 
Apteryx?. 
Other comparisons with the smaller existing Rallines of New Zea- 
land, notable either for loss or much reduced powers of flight, are 
carried out and well illustrated in the reduced figures (plates xx. and 
xxi.) of Prof. Jeffery Parker's memoir *. 
These have led me to believe that the accompanying figures, front 
and side, of the sternum of Notornis, natural size (pp. 690, 691), 
may not be unacceptable, as tending to complement the illustrations 
of the osteology of the extinct Ralline which have previously ap- 
peared in the Society’s publications’. 
In its sternal modifications the larger form, Aptornis, though 
strictly ralline in the sum of its osteology, has departed further from 
the existing forms. Not only have the “ postmarginal processes ” 
disappeared, with great reduction of breadth of sternum, but the 
place of a keel is indicated by a mere low obtuse ridge. 
Now, on the supposition that, with further atrophy of the pectoral 
muscles, the keel should disappear from the sternum and leave no 
trace, as it has done in several genera of birds otherwise structurally 
distinct, as, for example, in Struthio®, Rhea®, Dromaius’, Casuarius®, 
Apteryx®, and Dinornis”, are Aptornis and therewith Notornis to he 
? «Anatomy of Vertebrates,’ vol. ii. p. 24, fig. 15, e. 
° Trans. Zool. Soe. vol. ii. pl. 55. figs. 2 & 3. 
° Loe. cit. p. 245. 
* Trans. Zool. Soe. vol. iii. pl. 56. figs. 7-13; and vol. iv, pl. 4. figs. 5-8, 
° Trans. Zool. Soe. vol. iii. (1848), plate 57. fig. 4. 
6 1b. ib. fig. 5. 7 Db. ib. fig. 7. 
9 Trans. Zool. Soe. vol. it. (1888), plate 55. figs. 1-8. 
10 Trans, Zool. Soe. vol. viii. plates 7-9, 
8 Ib, ib. fig. 6. 
