oo 
PROFESSOR OWEN ON THE GENUS DINORNIS. 69 
Aptornis agrees with Apterya in the proportional extent of the antacetabular part of 
the ilium', but offers the same differences, and some of them exaggerated, which have 
been noted in the pelvis of Dinornis. In the general proportions, as in size of pelvis, 
the correspondence between Aptornis and Cnemiornis? is closer than between either of 
them and Dinornis; but there are differences of at least generic value. 
The anterior sacral centrums are relatively broader and less deep in Aptornis; there 
is no increase of breadth or expansion in the seventh or contiguous antacetabular ones, 
as in Cnemiornis; the narrowing is continuous, though quicker, after the seventh, in 
Aptornis, as far as the sixteenth, when the sudden expansion takes place. In Cnemiornis 
there is no indication of such expansion of terminal sacral centrums; they continue 
narrow and ridged below from the twelfth to the seventeenth. The breadth of the 
anterior sacral yertebra across the costal pits of the centrum in Cnemiornis is 7 lines, in 
Aptornis it is 13 lines; but the height of this vertebra must have been the same, or 
nearly so, in both. ‘There are surfaces for the articulation of a third pair of free sacral 
ribs in Cnemiornis; but these do not exist in Aptornis. The concavity of the pre- 
acetabular part of the ilium in Cremiornis is bounded above by a curved ridge, leaving 
a flatter tract between it and the summit of the bone; but there is no trace of this 
division of the bone in Aptornis. The posterior, horizontal iliac tract is divided by a 
median convex ridge in Cuemiornis, but by a deep median furrow in Aptornis. In that 
genus there is no trace of the superacetabular pneumatic fossa as in Cuemiornis, in which 
the acetabulum is relatively larger, its vacuity wider, its distinction from the posterior 
flat facet greater. The antischial depression of Aptornis is not repeated in Cnemiornis. 
In this genus there is no indication of the smooth, large, deep, hemispherical post- 
renal fossa on the under surface of the ilium which characterizes Aptornis; neither is 
there an iliac lamella bounding behind the interacetabular renal fossa. 
In both genera there are indications of similarity of the pelvis to that in Rallide; 
there is the length of the antacetabular part and its steeply inclined roof-like iliac 
plates, the great reduction of the iliac fosse through the non-extension, or slight exten- 
sion, of the ilia beyond the sacral diapophyses; but this affinity is more marked in 
Aptornis, as by the development of the postrenal ischial lamelle (P1]. XLII. fig. 2, v) 
and the small and round ischiatic foramen. 
§ 4. Notice of a mutilated Pelvis of Notornis. 
I have long entertained hopes of receiving, through the friendly cooperation of some 
collector of natural-history objects in New Zealand, materials for a monograph on the 
osteology of Notornis*; but, so far as I know, only a very few skins of that still lingering 
species of Ground-Coot haye hitherto reached Europe. 
* Compare Pl. XLII. fig. 1, 62, with Trans, Zool. Soe. vol. ii. pl. 54. 
? Compare the figures in the present Memoir with figures 5, 6, 7, pl. 64. Trans. Zool. Soe. vol. y. 
3 Notornis is affirmed to be living in considerable numbers in some districts on the west coast of the Middle 
Island (Mackay in ‘ Ibis,’ 1867, p. 144). 
VOL. VIL—PaRT v. January, 1871. 3 E 
