174 
posterior angles are hemispheric tubercles (1") as in P alapterys. The precondyloid 
holes (p, fig. 10) are nearer the carotid holes (ce, fig. 9) than m Palapterys, opening 
into the upper part of the same fossa. The occipital region inclines forward as it 
rises, and is defined above and laterally by a strongly marked ridge (2,3, fig. 10), which 
forms a slight angle above the base of the mastoid; the occipital surface is not divided 
by a median vertical ridge. In Porphyrio (figs. 1 & 4) the plane of the occipital fora- 
men inclines from below upward and backward ; that of the occipital surface is vertical ; 
it is proportionally narrower than in Notornis. 
The mastoid (8) gives off a short compressed angular tympanic plate (8, fig. 8). The 
fractured base (s’, fig. 9) of a process answering to that of the true mastoid process in 
other birds, and marked 8’ in the skull of the Aptornis (Pl. XLII. fig. 1), comes off 
from the lower part of the temporal fossa more in advance of the process 8, and rather 
as it would seem, from the alisphenoid than the true, mastoid. The same peculiarity 
is repeated in the cranium of the Porphyrio (Pl. XLVI. fig. 1, 8). The articular 
surface for the tympanic is divided, as in <Aptornis, into two subcircular cavities 
(y, y', fig. 9) by a pneumatic foramen. The parietal region (7, fig. 8) is singularly flat : 
the temporal fossz (between 8 and 12) unusually long ; well-defined by the ridge extend- 
ing from the paroccipital to the postfrontal: this process (fig. 7, 12) is short, obtuse, 
directed downwards and backwards; broader in Nofornis than in Porphyrio, The 
temporal fossa is equably divided by an intermuscular ridge (®, fig. 7) probably con- 
tinued upon a mastoid process as in Porphyrio (fig. 1, 8’). The whole inferior border 
of the temporal fossa is produced as a vertical ridge below the level of the adjoining 
basis cranii in both Notornis and Porphyrio, which gives a peculiar character to this 
part of the cranium. ‘his ridge (fig. 9, 8’) bounds the outer side of a large and well- 
defined muscular impression with intermuscular ridges extending from the anterior 
tympanic articulation (y) to the fore part of the base of the postfrontal (12). There isa 
similar muscular depression in the Porphyrio: in the Maccaw it is much shorter, by 
reason of the less antero-posterior extent of the temporal fossa. The fore part of the 
frontal, which extends beyond the cerebral cavity, and appears to have anchylosed with 
the base of the upper beak, has been broken away, exposing a fine pneumatic diploé 
(dl, fig. 8), and the olfactory outlet (ol, fiz. 11), which appears to have been common to 
both nerves ; but there is no trace of olfactory chamber at this part, as in Palapteryz. 
The chief singularity of the cranium, so mutilated, but with the cerebral cavity 
entire, is its regular four-sided figure ; the breadth of the fractured anterior part being 
almost that of the occipital region, and the extent of the sides being scarcely more than 
that of the front and back part. This character is very striking as we look upon the 
almost flat basis cranii (fig. 9), and is well-marked when the cranium is viewed from 
above (fig. 8), where a smaller flat square platform (7,11) is defined by the occipital and 
temporal ridges in the middle of the large square ; of which smaller square the anterior 
boundary is wanting, the platform here sloping gradually down to the base of the bill. 


