S4 
MR. W. K. PARKER ON THE STRUCTURE AND 
canals (see also figs. 3 and 4), are very conspicuous, shining through the hyaline 
cartilage. Outside the innermost lobe of the capsule, the ampulla and ascending part 
of the arch of the posterior semicircular canal ( p.s.c .) is seen, and in front of it, more 
outward, the hind part of the horizontal canal (h.s.c .), which arches over the incus. 
At present, the hind skull is a funnel-shaped structure, as though it were a 
detached and enlarged part of the spinal column. Along its wide floor, the basi- 
occipital region ( b.o .), the notochord (nc.) still persists, and runs more than halfway 
to the pituitary hole (py.); it enlarges somewhat whilst in the parachordal channel, 
and then ends in a point. Plight and left of its hind part, at a moderate distance from 
each other, the occipital condyles ( oc.c .) are seen to be sub-crescentic thickenings of the 
infero-lateral margins of the chondrocranium ; above and behind them, the roof ( s.o .), 
imperfect behind, is ossified by a median osseous centre.* 
The lateral occipital region (e.o.) is but little raised as a paroccipital ridge; it 
is notched for the 9th and 10th nerves (IX., X.)—the foramen being in the inter¬ 
space of the arch and the auditory capsule—and perforated a little further backwards 
and inwards for the 12th nerve (XII.). This would have been a pure chondrocranium 
but for the premature, single supraoccipital centre (s.o.). 
The upper view (fig. 2) shows the wide alinasal region ( al.n .) followed by the more 
contracted double tube of the aliseptal territory ( al.sp .), and this gradually widening 
into the aliethmoidal ( al.e .), which swells on each side of the face in front of the orbits, 
and contains the upper and middle turbinals. The pyriform cranium has the broad, partly 
ossified supraoccipital (s.o.) for its base, and shows the deficient chondrification (s.o.n.) 
over the foramen magnum (see also fig. 4). The fore margin of this convex wall is sinuous, 
concave right and left of the middle, but with a convex margin, there, on each side. 
The ethmoidal and supraorbital regions are covered with bony films; and also the right 
and left third of the most swollen part in front of the supraoccipital. Three pairs of 
these centres are visible from this aspect, the nasals, frontals, and parietals p.). 
The very small, short, nasals, are both in form, position, and relative size like those of 
a Bird, being deeply notched in front. But, in a Bird, these forks embrace the upper 
part of the external nostril, and between the nasals the premaxillaries send, each, a 
long lathy process—the nasal process (see in the Fowl, Phil. Trans. 1869, Plate 86, 
fig. 15). The Mammal has that process arrested, and the premaxillaries run under the 
outer edge of the nasals, and only have that extra-nasal process, large in certain types, 
e.g., the Hare and Rabbit. 
The frontals (fig. 2,/!) here lie over the orbital region, looking like the dislocated 
valves of a Bivalve ; they do not meet in the middle, above and in front; beyond their 
* A rare character—normal in Reptiles, "but as rare in Birds as in Mammals; I have only, as yet, 
found it in one genus of Birds, namely, Turdus —the Thrushes (see Monthly Microscopical Journal, 1873, 
plate 9, pp. 102-107). 
In this figure of the skull of the embryo Pangolin (Plate 11, fig. 1, s.o.) the roof with its bony tract is 
figured as it appeared in the flattened preparation; figs. 2-4 correct this. 
