DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
235 
hyals ( t.hy ., cornua majora—1st hypobranchials), separated from the base by cartilage, 
but not segmented off. 
Shull of adult Ericulus nigrescens. {Male.) 
The hinder half of the palatal view of the skull of this type has been figured 
(Plate 35, fig. 11); this is a very instructive skull, and typical of the Mascarene 
modification of the Insectivorous type; nearly typical, as respects the Order itself, in 
its modern development/'' 
The palatines (fig. 11, pa.) end in a straight line at the end of the hard palate ; 
they are behind the maxillaries, and have the well-formed pterygoids ( pg. ) attached, 
subvertically, to them. 
In the roof, the vomer (v.) is seen sheathing the perpendicular ethmoid, and the 
forepart of the presphenoid ( p.s .); the orbitosphenoids {o.s.) are not seen in this 
view, except a little in front of the great fissure (V 1, 3 .). Like the presphenoid, the 
forepart of the huge basisphenoid ( b.s.) is of moderate width, and flat; it is rendered 
somewhat concave by its union with the pterygoids. 
The sub -pituitary hollow is perforated, above, as in Centetes ; behind it the basi¬ 
sphenoid broadens out, and behind, both it and the basioccipital {b.o.) for some 
distance are subcarinate ; this ridge is due to the bulging of the earliest bone deposited 
round the notochord. The tympanic wings ( t.b.s .) are not symmetrical, that on the 
left side being much the larger of the two ; a notch separates these shells in front, 
from the equal and well-developed tympanic wings of the alisphenoid ( t.al.s .). These, 
with a similar process of the squamosals {sq.), form the antero-external outline of the 
obliquely oval tympanic spaces. These spaces are roofed, in front, by the same bones, 
and, behind, by the oblique, well-formed cochleae (c hi.). From those helices, to the fore 
edge of the great sphenoidal side gallery, out of which the 1st and 2nd branches of the 
trigeminal nerve (V 1,2 .) emerge, is a large space—half the cranial floor; it is an 
unmistakable Marsupial character. But the foramina are typical for an Insectivore ; 
this foramen ovale (V s .) is finished behind by the tympanic shell of the alisphenoid, 
and for a distance, in front, equal to its own width. Another oval hole of the same size 
is seen, but it has not its long axis outwards and backwards as in the foramen ovale, 
but inwards and backwards ; this is the hinder opening of the alisphenoidal canal 
(al.s.c.) ; the anterior opening being made into the common sphenoidal fissure or side 
passage. The squamosal {sq.) has a stunted zygomatic or jugal process, and a large 
oblique saddle-shaped glenoidal facet {gl.c.). Where the bone widens towards the 
tegmen tympani {t.ty.), and bounds the tympanic cavity, there is a short postglenoid 
tract and a small post-glenoid foramen. 
The external part of the ossified auditory capsule outside the tegmen has grown 
beyond its contained horizontal canal (compare with Microgale, figs. 1, 3, h.s.c.) into an 
* The original skull from which this figure was made is in the Biological Laboratory, South 
Kensington Museum. 
2 H 2 
