405 
border of the prezygapophysis (fig. 20, az) now begins to rise, and gives a more inward 
or medial aspect to the oblique articular surface. The postzygapophyses (fig. 21, pz, pz) 
show a corresponding change in the contrary sense, but they do not extend postaxially 
beyond the centrum in so great a degree as in Struthio!. A marked difference between 
the vertebree here compared is in the greater height and greater breadth of the neural 
spine in Dinornis; but the chief distinction is shown by the coexistence in Struthio of 
an independent or movable pleurapophysis with the first appearance of the single and 
simple hypapophysis. In Dinornis such condition of the hypapophysis is associated with 
a continued confluence of the riblet, p/. In other words, the single hypapophysis marks 
the first dorsal vertebra in Struthio * and the last cervical in Dinornis (fig. 18, hy). 
The character of the fifteenth cervical in the series of the skeleton of D. maximus 
is that of the sixteenth cervical in the neck-series of Hutton’s skeleton of D. ele- 
phantopus ; and this is followed by a seventeenth cervical, or one with anchylosed pleur- 
apophyses, beyond which there are seven vertebre for a dorsal series. But in both the 
sixteenth and seventeenth ceryicals the neural spine is bifid; the ridges from the 
hyperapophyses converge to the base of a single neural spine only in the first of the 
series of vertebrae in which the pleurapophyses retain their independence and mobility, 
If my series of cervicals in D. maximus be, as it seems by characters of juxtaposition, 
the correct number, Hutton’s specimen of the skeleton of D. elephantopus has two 
additional cervicals, in all seventeen, instead of fifteen as in Apterya. ‘These remarks 
are based on a photograph of the skeleton in the Otago Museum. 
In a cervical vertebra (figures 22, 23, 24) of D. giganteus, which I regard as homo- 
logous with the fifteenth or last cervical of D. maximus, the neural spine (fig. 23, ms) 
retains, as in D. elephantopus, its bifid character; but the parial portions are relatively 
less developed, and their connecting bar (ib. 6) has begun to mse, indicating, as it were, 
a rudiment of the single and longer neural spine in D. maximus. The hypapophysis 
(figs. 22, 24, hy) is single, and its base is supported by the ridges from the pleur- 
apophyses representing the ‘ catapophyses’ of Mivart. The posterior hypapophysial 
tubercles (ib. dy’) are better marked than in figure 19 (D. maximus). 
The neck-vertebre in every species of Dinornis in which I haye been able to deter- 
mine them correspond, with unimportant modifications, with those above described and 
figured, and in like degree differ from their homologues in Struthio. 
‘In the well-marked class of Vertebrates characterized by the many cervical vertebra, 
these, as a rule, are small; but in Apterya, and especially in Dinornis, they are excep- 
tionally large. Some of those in Dinornis maximus almost equal in size the neck- 
vertebrae of the horse. 
The muscular system, as has been shown in Apteryx (p. 44), is correspondingly 
developed; and when, to the proportionably still more powerful neck-muscles in 
| Comp. fig. 18, pz, with Mivart, loc. cét. p. 406, fig. 35. * Mivart, luc. eit. p. 408, fig. 40. 
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