DEVELOPMENT OE THE SKULL IN THE MAMMALIA. 
27 
above (fig. 7), and, lying prone on the under part of the face, the infero-anterior orbital 
foramen, through which a large branch of the maxillary nerve (V 2 .) passes, is well seen 
in the lower view. 
The palatine bones {pa.) are well developed, and they form two-fifths of the hard 
palate; their suture continues that of the maxillaries up to the front edge of the basi- 
sphenoidal region. 
In general form they, together, suggest the shape of the human thorax as seen from 
the front, and are overlapped by the maxillaries that form their shoulder. In front, 
they interdigitate with those bones, and then have each a foramen in their front 
fourth ; their “ waist ” is succeeded by a pair of small “ haunchesthese are the 
pterygoids {pg.), smallish, thick shells of bone, which partly floor the naso-palatine 
canal, but do not meet in the middle. The ascending processes of the palatines and 
pterygoids are not seen in this view, but they have been described in the sections 
(ls£ Stage). 
The orbital plates of the frontals ( f) are seen in this view, and also the bones that 
form the zygomatic arch ; these are the moderately large, but simple, jugal (/.), and 
the squamosal {sq.). 
Besides showing the crescentic, hollow glenoid facet {gl.f.), this view gives us a good 
idea of the secondary, splint-like character of the latter bone, stretching from the 
jugal nearly to the occipital arch ; it is beginning to be scooped out where it overlies 
the tegmen tympani {t.ty.). The hinder half of the endocranium is well shown in this 
view, obscured by no investing bones. In the openings of the orbits, below, we see 
the lateral ethmoidal masses containing the turbinals, and behind these the orbito- 
sphenoidal cartilage {o.s.), perforated by the large optic nerve (II.). Overlapping 
that wing, and itself overlapped above and outside, we see the alisphenoid {al.s.), a 
half-opened fan of thick cellular bone, the handle of which is separately ossified. 
Between the handle and the orbitosphenoid we see the sphenoidal fissure through 
which pass the orbital and maxillary branches of the 5th nerve (V 1,2 .), and the 3rd, 
4th, and 5th orbital nerves. 
In the hinder margin, behind the suture of the two centres of ossification, there is 
a large notch, becoming a foramen ; this is for the 3rd branch of the 5th nerve 
(V 3 .), and will be the foramen ovale. 
The basis cranii is winged here, for the lower bone, forming the handle of the 
fan-shaped alisphenoid, does not ossify close up to the median beam ; in that part, 
a little further backwards, a median bony centre, small and transverse, is seen; this 
is the basisphenoid ( b.s .); it is below and in front of the postclinoid w T all (see fig. 1). 
The organs of hearing are highly developed in the Armadillos ; here, right and left 
of the basis cranii, we see the huge cartilaginous capsules, with the special cochlear 
enlargement {chi.), larger, relatively, than I remember to have seen it in any Mammal 
of a moderate size ; of course it is, relatively, very large in the smaller kinds of Bats. 
in this view the cochlear bulbs {chi.), the tegmen tympani {t.ty.) outside each, and 
E 2 
