AXTAL SKELETON OF THE OSTRICH. 401 
to exhibit a special though slight prominence (directed medianly inwards and ventrad), 
which is the beginning of the differentiation of the catapophysis* (fig. 25, ¢). 
The metapophysis may be again slightly more prominent; while the /yperapophysis 
is so reduced that it would perhaps escape notice were it not traced from the more 
preaxial vertebre. 
The prezygapophysis projects beyond the parapophysis still less than in the fifth 
vertebra, sometimes scarcely or not at allso. Its articular surface is even also relatively 
longer and narrower than in the bone last described. 
The neural spine is excavated, both pre- and postaxially, more obliquely and ex- 
tensively than in the fifth vertebra; so that its median unexcavated part is relatively, 
and may be absolutely, shorter. ‘The lateral margins of the preaxial excavation do not 
at all develop preaxial processes. 
Both the pre- and postaxial margins of the neural arch are rather more concave than 
in the fifth vertebra. 
THE SEVENTH VERTEBRA. 
The seventh vertebra is rather larger than the sixth vertebra, but in other respects is 
so complete a repetition of the latter as hardly to need distinct notice except in the 
following few points. 
The catapophyses and metapophyses are rather more prominent; and the neural 
spine has (at least sometimes) a greater development dorsad. 
The prezygapophyses do not project forwards quite so much as do the parapophyses, 
instead of projecting, in a greater or less degree, more preaxially, as has always been 
the case in the vertebre hitherto described ; their articular surfaces are directed rather 
more inwards than are those of the sixth vertebra. 
Tue Erentu, Ninta, AND TENTH VERTEBRA. 
These vertebre slightly increase in length antero-posteriorly, though the rate of 
increase diminishes as we proceed postaxially. In these three vertebre the catapo- 
physial projection gradually becomes more marked; and thereby the preaxial part of 
the ventral surface of the centrum becomes more concave, as also the ventral margin 
of its preaxial surface. 
The metapophyses remain as marked (fig. 28, m) or become rather more so, while the 
hyperapophyses disappear. 
1 From xara, down. These processes are, as it were, merely transitional processes, sometimes merging with 
the parapophysis dorsally, and sometimes with the hypapophysis ventrally. By giving them therefore a 
distinct name I by no means wish to ignore their transition; but as these parts are often so distinct and 
conspicuous as to require description and distinct reference, it is convenient to be able to speak of them 
substantively and adjectively by a distinct term. By catapophyses I mean parts which are distinguishable 
from, but intermediate between, parapophyses and hypapophyses, and which are placed on the ventral side of 
the former. 
VoL. vilt.—Part vil. March, 1874. 3L 
