Head less flattened than in the _Dinornithidae_, much longer and narrower.
Brain case much greater in volume. Occipital condyle strongly pedunculate.
Temporal fossae deep and narrow. The basisphenoid has on each side a well
marked pterygoidal apophysis. The lower mandible is straight and stout,
recalling somewhat that of _Rhea_, but the maxillary branches are higher
and stouter. The symphysis is long, contracted, and hollowed out in the
shape of a ladle. The sternum presents many affinities to that of
_Apteryx_. It is a thin plastron, flattened, and much widened. The
coracoidal articular surfaces similar to those of _Apteryx_. The
Coraco-scapulars are feeble, and have so faint an articular surface that
the humerus must have been rudimentary. Hallux absent, outer digit has
five, the middle digit four, and the inner digit three phalanges.
There are three genera and twelve species.
A striking character is that in the genus _Aepyornis_ the proximal
extremity of the tarso-metatarsus is larger than the distal extremity, a
feature not found in the majority of other birds.
Monsieur Grandidier has expressly pointed out that _Aepyornis_ had only
three toes, I cannot, therefore, understand why Messrs. Lydekker and Evans
both state that the hallux is present. {222}
In spite of the researches of Messrs. Grandidier, Last, and Forsyth Major
and the large collections sent home by them, the number of _Aepyornis_
bones is infinitesimal compared with the vast masses of bones of the
_Dinornithidae_ contained in the museums. This paucity of material quite
prohibits us from making a critical study of the described species, so that
we are at present unable to say if too many or too few species have been
diagnosed. I am inclined, however, to think that if we ever get complete
skeletons of the larger forms, _Ae. grandidieri_ and _Ae. cursor_ will
prove to be sexes of one species, and also _Ae. titan_ and _Ae. maximus_.
For the present, however, the measurements are too different to allow of
their being united without further investigation.