234 
MR. W. K. PARKER ON THE STRUCTURE AND 
In the lower view (fig. 1 ), the foramen ovale (V 3 .) is seen just inside the stunted 
jugal process of the squamosal and the glenoid facet ( gl.c.), but the canal ( al.s.c.) is 
hidden by a lamina of bone, and the extremely outward position of the thin shell-like 
alisphenoidal wail is seen, and the crescentic notch that emarginates its oblique front 
edge. The huge alisphenoid—nearly as large as in a Marsupial—forms, behind the 
foramen ovale (V 3 .), an oblique strongly dentated suture with the inner edge of the 
squamosal, and then becomes hollow over the tympanic cavity, outside the tympanic 
wing of the basisphenoid. The hinder edge of that supratympanic lamina is deeply 
notched, and terminates close in front of the cochlea (chi.). 
The shell-like tympanic wings of the basisphenoid ( t.b.s .) reach as far forward as the 
foramen ovale (V 3 .) in front, and nearly to the fenestra rotunda ( fr .) behind ; they are 
manifestly “ bullae ” that have lost their distinctness from the basisphenoid, whilst the 
hollow cavity of the greatly extended alisphenoid is, as surely, the counterpart of the 
tympanic wing of that bone seen in Marsupials. The hollow, in front, under the 
basisphenoid, is present, but it is not so much marked as in Centetes; the rest of the 
basisphenoid is of an hour-glass shape and is somewhat carinate; its hind edge is 
bracket-shaped and is separated from the basioccipital ( 6 . 0 .) by a clear synchondrosis. 
The auditoiy capsules are ossified ; there is, however, some cartilage near the 
horizontal canal (fig. 1 , h.s.c.); this is the small epihyal ( e.hy.) in front of the 
foramen stylo-mastoideum (VII.). The cochlea (fig. 1 , chi.) is well formed, and the 
fenestras ( fs.o.,fr .) are seen outside and behind it, also the chink and channel for the 
facial nerve (VII.) emerging from the cranial cavity. The horizontal and posterior 
canals (h.s.c., p.s.c.) are seen on the outside, showing through their thin bony walls. 
Behind the posterior canal there is a bony ridge, and then a suture between that ridge 
and the short paroccipital process ( p.oc .). The basi- and exoccipitals (fig. 1 , h.o., s.o.) 
are confluent; the supraoccipital (figs. 1 ,4, s.o.) is a very large distinct shield of bone, 
cut away in a semicircle, over the huge foramen magnum ; the condyles ( oc.c .) are 
large, pyriform, and wide apart. 
The “ossicula,” separately figured on a large scale and seen from within (fig. 9), 
attached to the thick-rimmed middle-sized annulus (a.ty.), are worthy of note. 
The cartilage is gone in front and has left a large tongue-shaped processus gracilis 
(p-gr.), twice as large as the manubrium (mb.), and parallel with it. The body of the 
malleus is at a right angle with these handles, and is of great extent. Over and in 
front of its condyloid facet there is a large solid helmet of bone ; behind that facet the 
hind margin projects backwards as a rounded elbow ; and below the root of the 
manubrium there is a subglobular “posterior angular process” (ag.p>.) —a familiar 
Sauropsidian remnant. 
The incus (i.) and the stapes (st.) are large, well-formed, and quite typical. 
A small hypohyal (fig. 6 , h.hy.), equal to the epihyal (fig. 1 , e.hy.) above, is attached 
to a transverse basal bar ( b.li.br .), and from this proceed the two short diverging thyro- 
