152 MR. W. K. PARKER ON THE STRUCTURE AND 
external pterygoid plate. Behind the foramen the outer margin of the alisphenoid is 
notched, gently, and then grows outwards again to form a wedge, which is strongly 
jammed in between the squamosal and the petrous bone. Leading from the external 
pterygoid plate to this wedge, inside the foramen ovale, is an elegant crest of bone, 
concave, externally, and lying below the rough, dentated, hinder edge of the ali- 
sphenoid. This is the boundary line of the junction of the basal and alar osseous 
centres, and it is this tract which corresponds with the alisphenoidal part of the 
bulla of a Marsupial, the root of its so-called “tympanie wing.” This and the 
rest of the basisphenoid (b.s.) form a very peculiar structure, quite diagnostic of an 
Insectivore, and, when suppressed, tells of a departure from the normal skull of this 
Order. The fore part of the basal tract is pinched in so as to form a very narrow 
passage ; the hind part widens into a semioval concave space. Right and left of this 
space the basisphenoidal tympanic wings grow out; these are square tracts, notched 
and uncinate behind, and hollow, externally, where they add to the general drum- 
cavity. These hinder outgrowths of the basisphenoid are separated by a notch, 
externally, and by a groove continued from the notch, internally, from the pre- 
tympanic wing which has its homologue in the Marsupial. The cochlear part of the 
opisthotic (ch/.) articulates on its inner side with the basisphenoid, and in its outer is 
margined by the grooved tegminal tract which contains the horizontal semicircular 
canal (fig. 3, h.s.c.). Here the fenestra ovalis (/s.0.), fenestra rotunda (/‘r.), and the 
hinder opening of the groove for the facial nerve (VIL), bridged over by the epihyal 
(e.hy.), ave all displayed. 
The cartilaginous projection that contains the two front ampulle is separated by a 
bony tract of the opisthotic from the next cartilaginous swelling—the paroccipital 
(p.oc.); behind this the condyle (oc.c.) forms a third cartilaginous convexity. The 
broad, short occipital ring has its transversely oblong basal piece (b.0.) separated, still 
by a widish tract of cartilage, from the exoccipitals (¢.0.) ; these are bored by the 
12th and notehed by the 9th and 10th nerves (XII., [X., X.). 
The upper view (Plate 20, fig. 2) shows but little of the endocranium; but a dissected 
skull, shown in its lowev aspect (Plate 19, fig. 7), as far as the first third of the basi- 
sphenoid, displays several parts not yet described. 
In this preparation several of the lesser splint bones were left, in situ, and figured ; 
the premaxillaries (px.) are shown cut through their alveoli, horizontally, and we see 
that their palatine process is, at present, very short. But the front paired vomers 
(v’.) are close behind, and above, the sub-median part of those bones; they are long 
splints, a little scooped on their outside, and are in close contact with the pointed fore 
end of the vomer proper (v.), which runs in above them. Right and left of the paired 
bones (v’.) we see the large cochleate recurrent cartilages (7c.c.), and, outside these, the 
ossified inferior turbinals (7.tb.). The fore part of the upper and middle turbinals 
(u.tb., m,tb.) is ossified ; but the greater part of the wall and floor of this large bulbous 
labyrinth is still unossitied. The vomer (v.) is carinate behind its pointed fore end, 
al i il ee 
