362 PROFESSOR OWEN ON THE GENUS DINORNIS. 
vertical extent from the symphysis, where it is 63 lines, to the articular end; but the 
thickness of the rami, with the outer angular ridge and the curvatures, indicate adap- 
tations for strength in relation to powerful applications of the beak. And this accords 
with the massive character of the cranium, the extraordinary lever afforded by the 
transfer of the attachments of the recti capitis laterales! to the large basilar tuberosities 
carried down to so exceptional an extent below the bony junction of the head with 
the neck. 
The skull of Aptornis offers many and well-marked differences compared with that 
of Dinornis. The occipital condyle is larger, more hemispheroid, more prominent; the 
foramen magnum is narrower in proportion to its vertical extent (comp. fig. 2. pls. 10, 
12, 15, with fig. 1. Pl. XLI.); the paroccipitals are more outwardly and less back- 
wardly extended, the breadth there across exceeding that at the mastoids or at the 
postfrontals; in this particular Aptornis resembles Apteryx? and Notornis. But the 
angle or protuberance (PI. XLI. fig. 1, ¢) for the insertion of the portion of the “longus 
colli posticus” called “biventer capitis”® is more developed than in any bird’. The 
linear depression, indicative of the “coronal suture,” is more marked than in Dinornis. 
The mastoid process is smaller, but the premastoid much larger; and it adds by its 
bony union with the postfrontal another to the few exceptions (Zetraonide, Craa, 
Lophophorus, and some Psittacide) in which the Crocodilian character is repeated in 
the class of Birds. 
The “rhinal chambers”*’ are much smaller, absolutely and relatively, than in Dinor- 
nis®, and receive the olfactory nerves each by a single foramen instead of by several 
foramina. 
The basilar tract descends much lower before developing the tuberosities for the 
“‘recti capitis laterales;” and these tuberosities are larger, indicative of the great 
strength of those muscles and of the other “ recti”’ inserted into the marginal ridges 
and broad, deep, rough intervening surface of this extraordinary development. ‘The 
> 
basisphenoid contracts to a triedral process beneath the converging Eustachian channels, 
not present in Dinurnis, and the surface in advance of the basilar tuberosities is more 
vertical and compressed in Aptornis. The pterapophyses are rudimental and devoid of 
articular surface. The mastoidal articular cavity for the tympanic is divided or double, 
instead of being single as in Dinornis’; the upper condyle of the tympanic is corre- 
spondingly modified. ‘The tympanic has a premastoid process and articulation, not 
present in Dinornis; the squamosal articular cavity is not pedunculate; the surface for 
the mandible is single, not double as in Dinornis and most birds. 
‘ See Trans. Zool. Soc. vol. iii. pl. 35, 6, c. ? Tb. vol. ii. pl. 53. fig. 5. 
3 Tb. vol. iii. pls. 32 & 33, 0**. 
‘ This has no relation whatever with the superior or any other of the semicircular canals; it answers to the 
thickened part of the superoccipital ridge marked ep in Baleniceps (Trans. Zool. Soe. vol. iv. pl. 65. fig, 3). 
> Trans. Zool. Soe. vol. iii. pl. 52. fig. 5, is. 5 Th. vol. v. fig. 1, . 7 Tb. ib. fig. 1, w. 
