212 
MR. W. K. PARKER ON THE STRUCTURE AND 
its base are still cartilaginous, and the long crus of the incus ( l.c.i .) has its distal part 
attached. The opisthotic and epihyal (e liy .), at their junction, are cut through, and 
the continuation of that bar, unossified, into the ceratohjal ( c.hy .). The facial nerve 
(VII.) is seen escaping from the foramen stylomastoideum. 
Section 16.—In this section (Plate 30, fig. 15) more than half is figured; it shows the 
basis cranii (b.o.) cut through in the fore part of the foramen magnum ; the fore 
part of the condyles ( oc.c .) are in section; and the atlas and axis (at., ax.) also come 
into view. The occipital roof ( s.o .) is ossified above, and beloAv, runs ( s.a.c .) into the 
top of the auditory capsule over the anterior canal ( ct.s.c .). Below, the posterior canal 
( p.s.c.) is cut across; the thin, inner wall of the vestibule is ossified ; the thick outer 
part is still cartilaginous. 
Fourth Stage.—The skull of the adult Shrew (Sorex vulgaris). 
The interpretation of the skull in its perfect state will now be easy, in spite of its 
great unlikeness to that of an ordinary good-sized Mammal, or even of that of a 
typical Insectivore. 
Seen from above (Plate 31, fig. 1) the peculiar tenuity of this small skull is shown; 
the long bi-tubular snout ( al.n.) is half the length of the dorsal line of the ossified 
cranium. Laterally, however, the projecting premaxillaries (px.) protect the cartilage 
in its hinder third. The preorbital region and half the orbital, together, from one 
continuous bony growth ; faint signs only of the sutures between the nasals, frontals, 
premaxillaries, maxillaries. and lachrymals (n., f, px., mx., 1.) being visible. The tooth- 
sockets make the sides sinuous, and they only diverge, increasing the breadth very 
gently, up to the jugal processes of the maxillaries. 
The foramen infraorbitale (V 3 .) is very large, and well seen in this aspect; the space 
between the frontal and the jugal process of the maxillary is a sharp notch. From 
that notch to the general swelling of the hind skull the cranium enlarges but little; 
the upper part of the coronal suture runs straight across the middle of the skull-waist; 
it is well-toothed and somewhat squamous, the frontals (f.) being imbricated by the 
parietals (p.). The frontals are but little larger than in a Snake ; but in that Beptile 
the frontals remain distinct, whilst the parietals coalesce—just contrary to what takes 
place in this little Mammal. The parietals (p.) cover about four times as much space 
as the frontals, they are far from each other, and from all the surrounding bones, 
except the squamosal, in front. The saggittal and lambdoidal sutures are well¬ 
toothed, like the coronal; the general surface of the bone is smooth—polished, as it 
were—and gently convex. The fore part, helping to form the orbits, is narrow; the 
rest becomes almost twice as wide. Flanking the frontals the squamosals can just be 
seen, giving additional width to the temporal region. The middle half of the lamb¬ 
doidal suture has, set in it, a transverse plate of bone which projects forwards into the 
notched parietals in front, and lies straight along the fore margin of the supra- 
occipital (s.o.), behind ; this bone, which is slightly crested, is the interparietal (ip.). 
