238 PROFESSOR OWEN ON THE GENUS DINORNIS. 
Of the axis vertebra, the following are the relative dimensions in Dinornis parvus 
and D. maximus :— 
millim. millim. 
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The base of the centrum in Dinornis parvus develops a feeble submesial longitudinal 
ridge; its smooth fore ‘ preaxial’ articular surface is adapted to the hind surface of 
the atlas, but is transversely concave in the same slight degree in which that is 
convex; it is not divided by a non-articular depression, as in Dinornis maximus, 
from the convex articular undersurface of the odontoid (c). The ridge on the fore 
part of the hemal surface of the hypapophysis is not developed in D. maximus, 
but is so in Struthio, and in a greater relative degree in D. parvus. The fore surface 
of the ‘centrum proper’ is confluent with the hypapophysis and with the centrum 
of the atlas (odontoid process). The hind ‘postaxial’ articular surface of the 
second vertebra is convex transversely, concave vertically, the transverse convexity 
becoming feebly concave at the lateral borders, making a minor approach to the 
angular outline than in D. maximus. The hypapophysial process of the proper 
centrum of the axis resembles in shape and proportions that in D. maximus. 
The neural canal (figs. 8, 9, 2) is two thirds the length of the entire vertebra, and its 
width is one third of the breadth; the anterior outlet is subcircular, 8 millim. in 
diameter; the posterior outlet is transversely elliptical, 10 millim. across, and but 
6 millim. vertically. In D. mazimus the two diameters of this outlet are each 18 
millim. The parapophysis (ib. fig. 9, p) has not the same relative lateral extension 
as in D. maximus (loc. cit, fig. 7, p), the centrum of the axis in D. parvus being there 
relatively narrower. The rudiment of the pleurapophysis developed from the middle 
of the outer surface of the vertical bar completing the vertebrarterial canal in 
D. maximus (ib. figs. 5, 6, pl) is not present in D. parvus. From the diapophysial 
plate completing that canal, the small prezygapophysis is developed with an articular 
surface looking outward and slightly upward; the postzygapophysis (fig. 9, 2’) 
differs chiefly in size from that of the atlas. The neural spine isa strong and seemingly 
simple process ; but its summit is wanting. 
The succeeding cervicals retain the generic characters of those in Dinornis. But 
the main difference, as already remarked, is shown by their superior number, at least 
in the complete skeleton of the present diminutive Moa. 
The third cervical has a large compressed hypapophysis; but this abruptly subsides 
to a low ridge in the fourth, and disappears in the succeeding cervical, to give place, as 
it were, to the parial inferior processes which begin to be developed from the parapo- 
physes of the fifth cervical. 
In the third and several following cervicals the neural spine is represented by a pair 
