PROFESSOR OWEN ON THE GENUS DINORNIS. 386 
Between the origins of the trigeminal and vagal nerves in Pl. XLVI. figs. 1 & 2, are 
shown that of the “portio dura” of the seventh pair, and the origin of the acoustic 
nerve. 
§ 4. Cranial Cavity of Apteryx. 
I may here supplement a former Monograph on the Osteology of the Apteryx by a 
notice of the characters and foramina seen in the interior of the cranium. The largest 
of the foramina is the foramen magnum, which looks downward and backward. The 
cerebellar protuberance of the occiput projects a little beyond the foramen; it is 
bounded on each side by a venous canal, which, emerging from the cranium behind 
the petrosal, grooves vertically the occiput, and again pierces the bone at the upper 
margin of the foramen magnum. In most skulls of the Apteryx the right of these 
canals with its upper and lower holes is larger than the left. Near the lower border of 
the great foramen, on each side the condyle, is a minute ‘‘ precondylar foramen;” in 
advance and external thereto is the larger “‘ vagal” fossa and foramen. Above this are 
the minute foramina conducting the acoustic filaments to the labyrinth. These are 
overarched by a remarkable development of bone within the “tentorium,” forming in 
the dry skull a nearly horizontal plate, 3 lines by 1 line, terminating mesiad in a 
rounded and slightly thickened border. Beneath the back part of this plate is a large 
venous foramen. The superior semicircular canal raises a well-defined prominence on 
the petrosal platform continued into the above-described plate. The macromyeloual 
fossa is wide and moderately deep. It is bounded anteriorly by the posterior ridge of 
the trigeminal fossa and by the intervening hind wall of the sella. The foramen ovale 
leads from the back part, and the foramen rotundum from the fore part, of the fossa. 
The sella is deep and hemispheroid; it is tapped behind by the entocarotids. .The 
chiasmal tract rises vertically from its fore part with an irregular aperture on each 
side larger than is needed for the optic nerves. The chief peculiarity of the cranial 
cavity is the enormous rhinencephalic fossa, divided by the “lamina perpendicularis.” 
The dura mater closing these fosse is not ossified, so that in the dry skull the turbinals, 
upon which the olfactory nerves perforate the membrane to ramify, are here exposed. 
The cranial walls show a thin pneumatic diploé above the paroccipitals, but in the rest 
of the section they are thin and compact. 
§ 5. Brain of Dinornis. 
Returning to the brain of the Apteryz, the side view (fig. 1) is contrasted (in Pl. XLV.) 
with that of the Dinornis (fig. 11), the upper view (fig. 2) with fig. 12, and the under 
view (fig. 3) with fig. 13. 
The Dinornis differs in the minor relative size of the cerebrum to the cerebellum, 
which latter (figs. 11 & 12, ¢) rises wholly behind and uncovered by the hemispheres (). 
The cerebrum appears to be broader, because it is so much shorter, relatively, than 
that of the Apteryx; its upper surface is much more accentuated. A broad and high 
