150 
MR. W. K. PARKER ON THE STRUCTURE AND 
The jugals (j.) are flat styles; the squaraosals ( sq .), riding over them, are seen to 
swell out into a convex shell of‘ bone clamping the parietal, and then to grow 
inwards to be covered with the broadly-reniform glenoid facet ( gl.c .). The post¬ 
glenoid tract is here seen to bend in to the mastoid region of the ear-capsule, and to 
end in three tooth-like processes. 
Both the end view (Plate 19, fig. 6), and the inner view (Plate 1.9, fig. 8), also show 
the investing bones from their aspects. 
Endocranium of the Fifth Stage of Erinaceus europeeus. 
The vertical section (Plate 19, fig. 8) shows the whole of the craniofacial axis up 
to the presphenoid (ps.); behind, that the axis was cut along the middle, and only 
half the skull was figured ; this part is only two-fifths of the whole length. The 
round snout has its own septum marked off from the proper septum nasi (s.n.) by a 
considerable inferior notch, in which the Jacobson’s, or recurrent cartilages ( rc.c .) are 
seen to arise. These folded leaves are tubular in their most perfect j>art, and then 
are open along the side. 
Over the notch the intertrabecula (i.tr.) is very thick, but it diminishes very little 
all along the base of the great ethmonasal wall (s.n., p.e .); itis ossified behind by the 
orbitosphenoids ( o.s .), in the presphenoidal region ; there is no separate median bone 
there. 
The front paired vomer, and the vomer, proper, (v ., v.), are shown in situ; the 
nasals and frontals ( n.,f.) lie over the roof ( al.sp., al.e.). 
The short descending side of the low triangle formed by the great partition is 
notched by the numerous olfactory filaments, and the cribriform plate (cr.p.) is seen to 
the right of this crested tract, which has a small, special elevation, above—the crista 
galli ( cr.g.). 
The anterior sphenoid is still continuous with the nasal labyrinth, in front, by the 
fore edge of the great orbitosplienoidal cartilage (o.s .); the lower third of this tract 
is ossified, and is perforated by the optic nerve (II.) near its hind margin, below. 
The rest of that sinuous margin, passing into cartilage above, is now abruptly free, 
the rest of the band, over the alisphenoid, and along the supra-auditory region (see 
figs. 1-4) having been absorbed. 
Thus the sphenoidal fissure (V 1, 2 .) is now very steep, and perfect; it is bounded 
below by the cartilage still remaining between the fused orbitosphenoids (p.s.) and 
the distinct basisphenoid ( h.s .). The low-lying alisphenoid (al.s.) is free, in front, 
and bulges outwards; it is only notched in front by the 2nd branch of the 5th nerve, 
but is perforated by the 3rd branch (V 3 .), which forms a large foramen ovale near its 
hind third; this is much the smaller wing, even now. The basisphenoid is both long 
and wide ; over its hinder half the cochlea is seen ; the pituitary hole (see fig. 4) is 
present, but the sellar depression is slight. 
