2 SIE EICHAED OWEN ON THE STERNUM OF DINOENIS ELEPHANTOPUS. 



lines, suggests the attachment of a coracoid ligament. The cavity, fig. 2, at each end of 

 the anterior border, which received the articular end of the coracoid, is 1 inch 9 lines 

 in length, 1 inch in breadth. 



The costal tract, figs. 1, 2, 3, m, n, indicates the articulations of not more than two 

 sternal ribs ; whereas the sternum of the larger species (Binornis giganteus), described 

 in vol. iii. of the ' Transactions of the Zoological Society' (1848), p. 354, and figured in 

 plate lvii. fig. 1, showed a nearer resemblance to the sternum of the Apteryx (ib. fig. 8) 

 in the relative extent of the " costal border " (ib. fig. 3), and in the number, four, of 

 the articular surfaces for the sternal ribs. In the proportions of length to breadth the 

 sternum of Binornis elephantopus resembles that of Binornis giganteus. 



The articulation for the foremost of the sternal ribs in Binornis elephantopus (PL I. 

 fig. 1, m), is bent outwards and encroaches upon the outer aspect of the bone in a 

 greater degree than in the sternum of Binornis rhe'ides 1 . The rib, so articulated in 

 Binornis elephantopus, must have had a firm junction, the surface, m, being concave 

 in one (the longitudinal) direction, and as strongly convex in the other (transverse) 

 direction. The second articular surface, ib. n, divided by an interspace of 10 millims. 

 from the first, is of a simple oblong shape, slightly convex, 10 millims. in length 

 by 8 millims. in breadth. The lateral margin of the sternum, continued from this 

 articular surface, is at first thin and smooth, then thickens to a transversely convex 

 border, which is continued along the exterior of the lateral process, h. On the inner 

 side of the costal tract are two narrow oblong depressions, sharply bounded, mesially, 

 which are distinct from the above-described costal surfaces. If these inner facets aided 

 in giving attachment to sternal ribs, the articular ends of these would seem to have 

 been bifid. 



As the less complete sternum of Binornis elephantopus was represented by the inner or 

 back view in plate vii. of the above-cited volume, the subjoined drawing of the more 

 perfect bone from the outer side may not be unacceptable. 



To the hinder extremity of the body of the sternum — broken off in the subject of 

 plate vii., torn. cit. — the more complete specimen here described shows there a mesial 

 notch, answering, probably, to that which indents the narrower and more prolonged 

 " xiphoid " end of the bone in Binornis rhe'ides (torn. cit. plate viii. fig. 1, g). It may 

 be that the notch, g, in Binornis elephantopus, is the anterior border of a foramen, 

 answering to that in advance of the terminal notch of the rhe'ides s sternum ; but I deem 

 the first interpretation the more probable one. 



The feeble convexity of the outer surface of the body of the sternum subsides at the 

 hinder half to flatness. The total breadth across the ends of the lateral processes is 

 1 foot 1 inch. The breadth of such process at its base is 40 millims., at the broken 

 end 23 millims. ; the inner margin of this long process is trenchant to near the end of 

 the fracture, where it begins to thicken. 



Trans. Zool. Soc. vol. vii. plate viii. tig. 1, m. 



