222 MR. W. K. PARKER ON THE STRUCTURE AND 
fenestral bar between the fenestra ovalis and the fenestra rotuada (fs.0., Jr.) ; above 
(fig. 5, op.) it has formed a roughly erescentic shell round the inside of the meatus 
internus (VIL, VIII.). On the inside, the great anterior canal (a.s.c.) arches over the 
large but shallow fossa for the ‘floceulus” (/l.7.); the convexity behind this fossa is 
formed by the sins, common to the anterior and posterior canals. Below (fig. 4), the 
horizontal and posterior canals are seen. These views have, however, to be corrected 
by the other figures (figs. 1-3) when the parts had not been subjected to pressure. 
Above (fig. 1), the top of the huge auditory convexity is seen, and then the posterior 
canal (p.s.c.) can just be seen where it has passed away from the anterior, 
On the side (fig. 3) all the three canals (a.s.¢., /.8.c., p.s.c.) are seen, showing through 
the hyaline cartilage, in their natural position, and leaning backwards: a normal state 
of things for a Mammal. 
Below (fig. 2), in the undisturbed condition of all the cranial elements, the 
horizontal and posterior canals (h.s.c., p.s.c.) come well into view and meet at a right 
angle. But the ampulla of the horizontal canal is, here, hidden by the epihyal (e.hy.), 
which is confluent with the capsule, and by the facial nerve (VII.) passing through 
the stylomastoid foramen. 
The occipital arch must be described from the figures of the complete skull (figs. 1-3) 
as well as from those of the outspread endocranium. The keystone (figs. 1, 2, s.0.) is 
very large, and its evenly emarginate fore edge is adapted to the hinder round edge 
of the still larger interparietal (.p.). The cartilage is wide between it and the 
exoccipitals (e.0.), and they are separated by a tract, half their own width from the 
polygonal basioccipital (b.0.) whose hind margin is notched to form the fore boundary 
of the large foramen magnum (f-m.). The occipital condyles (o0c.c.) are long-oval in 
size and shape, and are moderately convex. 
The foramen condyloideum (XII.) just behind the chink for the 9th and 10th nerves 
([X., X.) is through the thick cartilage in the lower edge of the ex-occipital. 
The deep mandible (mk.) in its proper mandibular part, inside the superficial 
“ramus” is now invested, roughly, with bone, possibly derived from the dentary (d.). 
Under the condyloid process of the ramus (cd.p.) the proximal part of MrcKe.’s 
cartilage has acquired a styliform ectosteal plate, and this is spreading over, and 
growing into, the head of the malleus (m/.) nearly up to the articular condyloid facet 
for the incus. That facet is deep and selliform ; below it, the hinder margin of the 
malleus is semicircularly notched, and has an unciform angle. 
From this angle, and from the lower edge of the bony centre, the main enlargement 
grows obliquely forwards ; it then dips to form a subglobular posterior angular process 
(p.ag.) from which the manubrium (fig. 7, mb.), arcuate and dilated at its free end, passes 
forwards. The incus (7.) is perfectly normal ; its straight, conical “short crus” (s.c.2.) 
is large, and its “long crus” (/.c.7.) is thick, well inturned, and hasa short-oval orbicular 
plate for the stapedial head ; the body of the incus is rapidly ossifying from the hinder 
concave margin. The stapes (st.) is very short, has an almost circular fenestra, and 
