DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 239 
temporals (p., 7.p., s.t.), but it scarcely shows the squamosal (sq.) ; the form of the skull 
thus seen is reniform, with the hilus below, and is gently convex, with many 
sinuosities. 
Endocranium of Microgale longicaudata. 
I have no inner views of this skull, but through the huge foramen magnum 
(fig. 5, fim.) the large eribriform plate is seen to have two deep antero-superior 
recesses ; and the orbitosphenoids to be pierced by the optic nerves in the middle of 
their basal regions ; the shallow sella turcica, and the deep recessus flocculi, in the 
auditory capsule, can also be seen thus, without injury to the prepared skull. 
At this point and that the endocranium can be seen from without (Plate 35, 
figs. 1-5). The nonsegmented deflected snout, with its sublateral nostrils (a/.n., e.n.), 
is exposed ; but the form of the true olfactory region can be traced and seen through 
the semitransparent frontals. The orbitosphenoid (figs. 1, 3, 0.s.) is seen but little in 
any of these figures ; the optic nerve (fig. 3, I1.) is shown as emerging in front of the 
great sphenoidal side-passaye, out of which escape the 3rd and 4th, the Ist and 2nd 
branches of the 5th, and the 6th, nerves. The alisphenoidal canal (a/.s.c.) is short and 
its anterior opening, although less perfect than in the Dog, is plainly shown by a 
deep notch in the front of the alisphenoidal wall (a/.s.); the foramen ovale (V*.) is 
well seen both in figs. 1 and 3, laterally ; the suture between the alisphenoid and 
squamosal above (fig. 3, a/.s., sq.) is indistinct. In the basal view (fig. 1) the whole 
posterior sphenoid is displayed, a structure equally elegant and instructive. The sub- 
pituitary hollow is obsolete, the basisphenoid running backwards as a rounded balk 
from the presphenoidal, up to the basioccipital, region (fig. 1, p.s., b.s., b.0.). 
Behind, in the latter region, the exposed part of the bone is a mere chink, owing to 
the proximity of the tympanic wings of the basisphenoid, which almost touch, back to 
back, like the aliseptal cartilages of the nasal labyrinth. These shell-like periosteal 
outgrowths (exogenous ‘ossa bulla”) are broad, notched, and out-turned in front ; 
behind, they are pointed, and the last third of the strong aponeurosis is not ossified ; 
so that these wings (or shells) do not finish the floor of the large tympanic cavity, but 
a large membranous space is left, bounded by the annulus in front, the bony ala inside 
the occipital arch, behind, and the mastoid process (op.) externally. On the other 
side, where the annulus has been removed, and the cochlea (ch/.) exposed, the imper- 
fection of the bony floor of the skull is seen. In front of the large auditory region 
the skull has a very fenestrate appearance, the two openings of the alisphenoidal 
canal (a/.s.c.) and the large foramen ovale (V*.) cause this. The alisphenoids do not 
end after letting out the 8rd branch of the trigeminal nerve ; a thick bar of bone runs 
across behind the foramen ovale, this is continuous, now, with the basisphenoid within, 
and supplemented, externally, by a similar wing or bar of the squamosal (sq.). This 
bony boundary of the drum-cavity is continued backwards by the outer (tegminal) edge 
of the squamosal, so as to form, roughly, a quadrant, which ends close in front of the 
