56 
MR. W. K. PARKER ON THE STRUCTURE AND 
right is larger than the left. Longitudinally, in the hard palate, the palatines (pa.) 
are half as long as the maxillaries, but their semicircular hind margin is but a short 
distance from the end of the alveolar tract of the maxillary. The thick outer part, 
forming a wall to the naso-palatine passage, projects outwards, and is notched behind 
for articulation with the pterygoid (pg.). The upper transverse flange of the palatine, 
which articulates with the presphenoidal cartilage (p.s.), is followed by a similar plate, 
belonging to the pterygoid, which binds upon the bony basisphenoid. The descend¬ 
ing part of the pterygoid is nearly parallel with its fellow ; die two continue the 
naso-palatine wall, but are not so solid— in this species —as the corresponding tract of 
the palatines ; the hook or “ hamular process” is blunt, free, and capped with hyaline 
cartilage. 
Through the badly-enclosed orbital space the orbital plate of the frontal can be 
seen, but much less than in the Unau embryo (Plate 8, fig. 1). Outside, the large 
squamosals ( sq .) flank the greater part of the hind skull; they have a considerable 
temporal tract binding on the alisphenoids (al.sf outside which there is a large 
glenoid facet (gif), protected externally by a thickish zygomatic process, which projects 
forwards more, and is sharper than that of the other kind (Plate 8, fig. l). Behind 
the glenoid region the squamosal bulges outw r ards, greatly increasing the strength of 
the auditory region ; it reaches, behind, to a point over the stylomastoid foramen 
(VII.). Abutting against this posterior tract of the squamosal are seen the two back- 
wardly-turned horns of the large annulus tympanicus (a.ly.), a bone which, even now, 
is a broadish shell, with a dentated inner margin. Both really and relatively, these 
“ rings ” are much larger than in the other kind; in both they are large, relatively to 
the size of the skull; but in this kind they cover the cochlea (chi.) much better. 
Much of the endocranium is visible in this aspect. In the fundus of the orbit the 
unossified top of the orbitosphenoid and the optic nerve (o.s., II.) are shown, then 
the sphenoidal fissure (V 1, 2 .), followed by the large, thick, ossified alisphenoid, notched, 
above, for the third branch of the 5th nerve (V 3 .). In the middle, the broad basisphe¬ 
noid (b.s.), notched in front and concave behind, lies behind a tract of cartilage, which 
narrows forwards ; this is the presphenoid (p.s.). The synchondrosis is less than half 
the extent of the basisphenoid ; then comes the basioccipital (b.o.), one-third larger 
than that bone, imperfect in front, and alate and sub-triangular behind. The apex of 
the triangle is notched, for there the bone forms a small part of the outline of the 
foramen magnum ( f.m .). The rest of the occipital arch is but little seen in this 
aspect ; but the large condyles ( oc.c .), the postauditory and condyloid foramina (IX., 
X., XII.), the interspace of cartilage between the basioccipital and the exoccipitals 
(b.o., e.o.), as large as these centres, right and left, and the edge of the supraoccipital 
cartilage (s.o.), behind the foramen magnum, are clearly shown. 
A widish crescentic tract of cartilage, the inner face of the cochlea (chi.), is seen 
inside each “ annulus; ” and, opposite the fore end of the basioccipital, the Eustachian 
opening (eu.), a lipped, crescentic slit in the inner and front face of the tympanic 
