172 PROFESSOR OWEN ON THE GENUS DINORNIS. 
This specimen of sternum is now in the Museum of Science and Art at Edinburgh, 
and has been kindly confided to me for the purpose of the present memoir. It 
agrees in general characters with that of Dinornis elephantopus', but with specific 
differences. It shows the articular cavities (Pl. XXXII. fig. 5, b, 6) for the coracoids, 
the two costal borders (figs. 3 & 4), and the hind border entire. The latter, besides 
the two lateral deep and wide emarginations (f, /), has a small and shallow medial 
one (g, g). A similar, but smaller, yet relatively deeper, medial notch characterizes the 
corresponding part of the hind border of the sternum of Dinornis rheides?. 
This three-notched type of hind border is, so far as I know, unique, or peculiar to the 
sternum of Dinornis. 
The specimen under description (Plate XXXII.) is more convex externally, more 
concave internally, than in Dinornis elephantopus, as represented by the subject of 
plate vii. (tom. cit.). The anterior border is bent inward? or upward, and mainly 
defines the deeper part of the concavity on that surface (fig. 2, a). The integrity of 
that border with its terminal costal processes (d, d) shows it to describe a feeble curve 
concave backward (fig. 5). It is smoothly rounded, and about half an inch in thick- 
ness ; its extent in a straight line is 8} inches. 
An accidental or individual loss of symmetry distinguishes the present specimen. 
The right cavity (fig. 5, b) for the coracoid is deeper and better defined than the left 
(ib. '). It would seem that the chief work of depressing the sternum in inspiration had 
fallen to the right scapulo-coracoid bone, and that in this act the inspired air had been 
driven with more force into the left sternal air-cell or reservoir, an act which had been 
so long or so often repeated as to have pressed the corresponding part of the sternum 
more outward than on the right side, resulting in a deeper inner concavity (ib. fig. 2, pn) 
and more prominent outer convexity (ib. fig. 1, s) on the left half of the fore part of 
the bony plate. On its opposite surface the number of small pneumatic foramina is 
greater, and they are somewhat larger in the deeper left depression than in the 
shallower right one. 
The lateral borders of the inner concavity are formed by the extension inward of that 
margin of the costal tract (¢, ¢), especially at the second and third articular surfaces. 
The outer border near the first or anterior costal surface projects externally. About 
one inch and a half of the end of the left lateral process seems to have been, in the 
bird’s lifetime, broken from that process, and subsequently reunited to it (at h’, 
figs. 1 & 2). 
It is interesting to remark, in connexion with the abrogation of the wing-bones and 


maximus haying been so discovered in relation therewith as to justify Dr. Haast’s determination, and by the 
agreement of such mutilated sternum with the answerable parts of the entire specimen. 
‘ See plate vii. Zool. Trans. vol. vii. 1868, p. 115. 2 Th. plates vii. & ix. g. 
® See ‘ Note,’ p. 116, in mem. cit. 
