292

262

MEMOIR

ON THE

MODIFICATIONS OF THE SKULL

IN THE

GENUS DINORNIS.

----------------------------

In the Memoir on the skeleton of Dinornis elephantopus, the skull is briefly noticed
(p. 233). Subsequent acquisitions of specimens of that pPrt, in some respects more
complete, enable me to better appreciate its specific characters and to bring them out
by comparisons with those of the skull of Dinornis robustus, described pp. 151-169.
I also avail myself of those grounds to determine and elucidate the cranial characters
of some other species of Dinornis, as well as those of the seemingly dinornithoid gigantic
bird which, like Gastornis parisiensis, existed in our own part of Europe at a remote
tertiary period.

Skull of Dinornis elephantopus. ( Plate LXXVII. )

The cranium of Dinornis elephantopus equals in length that of D. robustus 1, but is
inferior in breadth and more convex both longitudinally and transversely, especially the
latter, at the interorbital region (fig. 3, 11). The entire skull of D. elephantopus is
shorter than that of D. robustus, by reason of the relatively shorter premaxillary and
mandibular bones.

The occipital condyle (Pl. LXXVII. figs. 2, 4, i) is a hemispheroid with a small pro-
portion truncate above, from the middle of which surface a groove extends to the
centre ; its breadth is 4 1/2 lines, its vertical diameter is 4 lines.

The occipital foramen is in one skull subcircular, in others shield-shaped, as in the
second specimen of D. robustus (Pl. LV. fig. 2). The lower transverse superoccipital
ridge (Pl. LXXVII. fig. 2, 2), which overhangs the foramen, subsides upon te exoc-
cipitals sooner than in D. robustus. The basioccipital descends proportionally lower to
its bimammillate union (ib. figs. 2, 4, 1') with the basisphenoid. There is one small precon-

1 Measured from the superoccipital protuberance to the premaxillary depression on the nasals ; comp.
Pl. LXXVII. fig. 1 with Pl. LXIV. fig. 1.