428

398

of the centrum. The haemal depression (fig. 13, c) behind the preaxial surface (ac) is
deeper than in the third cervical ; and the angle between this and the hind half of the
centrum, c, owing to the non-development of the hypapophysis, is more marked. The
spine (fig. 12, ns) repeats its small basal extent and bifid character.

The diapophysial plate (fig. 12, d) extends its origin from the outer side of the
prezygapophysis, z, halfway towards that of the postzygapophysis, before it bends
down to coalesce with the pleurapophysis, pl ; the broad outer wall of the vertebrarterial
canal (fig.13, v) thus formed is the 'pleurapophysial band' of Mivart 1. It sends
forward from its lower anterior angle a short obtuse parapophysis (fig. 12, p). The
riblet, pl, extends backward from the opposite or hinder angle. The vertical hind
border of the 'band' has two semilunar insertional impressions, the angle (fig. 12, a)
between which is less produced than in Struthio.

The pleurapophysial bank has a relatively greater vertical extent than in Struthio ;
and this relates to the corresponding excess of vertical over longitudinal dimensions in
the entire vertebra of Dinornis as compared with Struthio.

In the direct under view (fig. 13) the pleurapophysis extends almost to the vertical
level of the postzygapophysis, z' (compare with fig. 24, Mivart, loc. cit.) ; a more
marked difference from Struthio is in the bifid neural spine of Dinornis. There is no
medial hypapophysial ridge in D. maximus.

In D. elephantopus the fourth cervical has the hinder half of the lower surface of the
centrum relatively wider than in fig. 13, c' ; the prezygapophyses are less produced
forward than in fig. 12, z.

Glancing along the cervical region, in the articulated skeleton of Dinornis maximus,
one sees, as in that of D. elephantopus, that the two (parial) neural spines continue to
be developed throughout that series of vertebra, the uniting basal band subsiding some-
what in the fifth cervical, and each spine being then represented by a ridge continued
forward from the hyperapophysis, converging toward its fellow as it rises ; but it
attains no great height in any vertebra. In the fourteenth cervical, where the parial
neural spines are most marked in this respect, the uniting base gains in vertical extent.

The parial hypapophyses ('catapophyses,' Mivart) commence at the fifth cervical as
low tubercular ridges. they come nearest to each other at the fourteenth, but do not,
in Dinornis, circumscribe a haemal canal in any vertebra 2. In the fifteenth cervical the
parials combine to form a single medial hypapophysis near the middle of the length of
the under surface.

In one skeleton of D. elephantopus this coalescence takes place at a sixteenth cervical,
the antecedent series having one more vertebra than in the skeleton of D. maximus
here described.

1 Loc. cit. p. 398.
2 Comp. with this modification the cervical vertebra in the Flamingo (Owen, 'Anat. of Vertebrates,' vol i.
p. 29, fig. 20, h).