256 
MR. W. K. PARKER ON THE STRUCTURE AND 
seen above, behind the cribriform plate, which is the end of the perpendicular ethmoid, 
and the beginning of the presphenoid. All the fore part of the basis cranii on the 
under surface (fig. 1) up to this point is hidden in the lower view by the vomers. In 
the upper view (fig. 2) the orbitosphenoids have lost their large cartilaginous upper 
part, and now form two oblique, four-sided wings (o.s.) that have met, and largely 
coalesced below, to form a long presphenoidal region, as in the Hedgehog and the 
Mole; the Shrew, as I have shown, agrees with the Marsupials in having an 
independent presphenoid ; that is a rare thing among the Eutheria, but is seen in 
small Rodents. The optic foramen (II.) is very large—a good Lemurine character— 
and the bar enclosing it, behind, is strong; here we are far away from the Mar¬ 
supials. There is still much cartilage between the presphenoid and basisphenoid ( b.s .); 
the fore margin of the latter is bilobate, and its sides show some remnants of the 
expanded parts that in typical Insectivores form the tympanic wings ; there are two 
irregular knobs on each side. The alisphenoids ( al.s.) are still distinct from the basi¬ 
sphenoid, they are one-third larger than the orbitosphenoids, and overlap them by 
their inner and anterior angle much more than in Bhynchocyon and the Marsupials ; 
this corresponds with what we see in Bats, but is quite unlike the peculiar over¬ 
lapping growth of the alisphenoid in typical Insectivores. Each wing is ear-shaped, 
narrowing in behind, and so deeply notched for the 1st and 2nd branches of the 5th 
and the orbital nerves in front (V 1 . 2 ), and by the 3rd branch (V 3 .) behind, that there 
is only an isthmus of bone one-third the extent of the wing between the two great 
round notches ; this is equally true of these parts in a young Pteropus. When the 
soft tissues are removed between the posterior sphenoid and the auditory capsules 
(fig. 2), then a very irregular middle lacerated foramen is seen, this is bounded postero- 
laterally by the squamosal (sq.). That bone covers nearly all the auditory capsule, 
externally (Plate 38, fig. 1 , sq., op).), and below (Plate 39, fig. 1 . op.), only a small 
mastoid tract is seen clamped by the squamosal, perforated by the facial nerve (VII.), 
and having in front of that foramen (stylomastoid), a very small rough bony elevation, 
the arrested and confluent epihyal ( e.liy.). There the bony capsule is pinched, for the 
exoccipital (e.o.) nearly meets the squamosal in front of the epihyal knob. Then the 
auditory labyrinth expands, running inwards and forwards, and showing, from behind 
forwards, the heart-shaped fenestra rotunda, the oval fenestra ovalis, and the notch 
in front of the latter, through which the facial nerve (VII.) passes to get under the 
tegmen tympani (t.ty.) ; the whole fore and under part is the smallish, obtuse cochlea 
(chi). 
Above (fig. 2), the capsule is well displayed; it has a rough keel in front of the 
proximal cochlear eminence, behind which, running inwards and a little back-wards, 
are several holes. The porched meatus interims, on the inner side, contains several of 
these, the outermost being for the facial nerve (VII.) and the other for the auditory 
or portio mollis (VIII.). The former passes under a thick bridge of bone, and then 
runs round and escapes through the notch in front of the fenestra ovalis (fig. 1 ,fs.o., 
