664 
ME. W. K. PAEKEK ON THE STEUCTUEE AND 
face of the reverted oblong quadrate mass. It leaves the junction of the tegmen and 
otic process uncovered, has a scooped margin, where it binds against and then retreats 
from t the stapedial encircling ring ; it then, by steps, reaches the hinder face of the 
quadrate, leaving its margin uncovered, but it well enwraps it further forwards, down 
to the condyle, and round its front edge, ensheathing it by a beak-like folded plate. 
This is not all, for the middle of its outer face is hollowed into a valley which is bridged 
over by the columella ; and this valley ends in front in an outstanding basin, suboval in 
shape, but apiculate, and with a fixed base. This cochleate process of the squamosal 
has its edges lined with the almost perfectly circular annulus, whose open part is tra- 
versed by the mediostapedial. The apex of the scooped squamosal process projects in 
front of the annulus ; its cavity contains air, which it derives from the Eustachian tube, 
this part being built in the first postoral cleft, and utilizing, as it were, that old chink 
for these new auditory purposes. Behind the ethmoid, and in front of the auditory 
masses, the chondrocranium soon dies out ; the parasphenoid has a bevelled upper edge, 
and the fronto-parietal slab has a raised and thick superorbital ridge, and a large, low, 
slanting orbital face (fig. 4 , pa.s., f.). In front the frontal dips into a thick antorbital 
process (figs. 1 & 4 ,f.), which is overlapped by the large nasal (n.). 
This huge fibrous frontal is very ichthyic ; it is divided into three processes in front, 
the antorbital and ethmoidal processes, the outer broad, and the inner sharp. In the 
very middle it is hollow, and from thence there run a small groove directly forwards, 
and a pair of deep grooves obliquely along the antorbital lobes. Behind there is a low 
thick ridge with crescentic scooping at its sides. Narrowing from the antorbital s it then 
sends out a short thick postorbital process ; from that part the parietal region (jj.) 
narrows, by steps, between the auditory masses, to overlie the occipital arch. 
Half as much space is covered by the imbricating “ nasal ” wedges (n.) ; these are 
large, roughly triangular bones, with rounded corners and a notched outer margin ; this 
notch, nearer the inner than the outer angle, is for the external nostril ( e.n .). The 
nasals are gently convex above, and very fibrous. Running along their outer margin 
(figs. 1, 4, 7) we see under their edge the preorbitals ( jp.ob .) and the septo-maxillaries 
(s.mx.) ; the latter are now seed-shaped and fiat, and bordered by the remains of the 
larger upper labial ( u.l .) ; the former are flat, much larger than the septo-maxillaries, 
and ending behind in an inturned sharp hook. As the nasals meet above, in the front 
part (fig. 1, n.), so the premaxillaries meet below (fig. 2 , jpx.) ; they, like the maxillaries 
(mac.), are entirely on the under surface. Together, the premaxillaries have the form 
of the letter W ; they have each a pyriform outline, with a sharp stalk, the palatine 
process. A similar process grows from the maxillary (mx.), as this bone overlaps the 
premaxillary in front and joins it by a sinuous margin. The anterior part of the rounded 
and thickish outer edge of the maxillaries help the others to make a semicircular outline 
to the front of the face ; but the maxillaries then bend in, and as gently bend out again 
where they have met the pterygoids. Their jugal process is a pointed spatula, which 
lies obliquely beneath the leafy part of the pterygoid, in its groove. The eyeball ( e ) 
