DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 
71 
behind the middle of the basisphenoid, it is gently concave, as the roof of the hind 
part of the very long naso-palatine canal. 
The rest of the basal region, formed by the basioccipital ( b.o .) is very large, and 
between pentagonal and orbicular in shape ; and like that of the Unau (Plate 9, fig. 1) 
has a very Sauropsidan form and size, but still more so than in the Sloth. As in 
that type, the bone has strong “ basipterygoid processes ” (figs. 4 and 9, b.pg.), which 
functionally correspond to the parts so named in the Sauropsida, but are, here, the 
outgrowths of a hinder bone. Here they reach within a short distance of the rim of 
the foramen magnum (figs. 1, 4), and are, indeed, as strong and well-developed as any 
of their analogues in Reptiles or Birds.' 1 ' 
In the sides of the hind skull, as seen in this under aspect, the parietals (p.) come 
into view, outside the squamosals (sq.), a rare character, and one that can only occur 
in such a curious gourd-shaped skull as this, or hr the similar skull of the Pangolin— 
next to be described. Inside them, the abnormally small squamosals (figs. 1 and 9) 
make a better figure in this under face of the skull than they do as seen from the 
outside (fig. 3). The zygomatic process is very stunted, and behind it w T e see the 
small pyriform gently concave glenoid facet (gif), with its narrow end forwards and a 
little turned outwards. 
Hie postglenoidal part of the bone curls inwards, but is notched in the middle, 
iust in front of the tegmen tympani and ossicula auclitus, and where the hollow bone 
has its pneumatic passage opening into the cavum tympani. A large sinuous under 
and inner flange runs from the convex outer part of the squamosal, and strongly 
undergirds the alisphenoid; it almost reaches the basicranial plate of the pterygoid 
(pg.), and is, in turn, itself undergirt by the fore horn of the large bony annulus 
(a.ty.), and also by the large spatulate processus gracilis of the malleus (fig. 9, p.gr.). 
A small vascular foramen is seen at the posterior angle of the squamosal (see also 
fig. 3, sq.). 
The tympanic annuli (a.ty.) are quite comparable to those of the embryo of the Ai 
(Plate 8, fig. 5), as to their large, relative, size. The side view (fig. 3) shows them, 
but not so well as this ; them aperture is wide, and obliquely turned outwards and 
forwards, and is occupied by the manubrium and ear-drum skin (tn.ml., m.ty.). The 
part round the run of the opening is smooth, convex, and is taking on the well- 
marked bulliform character seen in the adult. All round the horns and convexity, 
externally, they are notched, or toothed, in a remarkable manner. Behind these 
bones, the ossified auditory capsule (op.) comes into view, with the opening for the 
9th and 10th nerves (IX., X.). This skull is somewhat more advanced as to its 
# The quasi-embryovic arrest of the hinder hard palate in this kind is very instructive; a little more 
energy of growth would have given this dwarfed, arrested, Anteater, with its long pretensile tail for the 
service of its timid, arboreal life, a palate equal to that of its larger congeners (compare fig. 1 with 
Professor Flower’s figure of the basal view of the skull in the Ant-bear; ‘ Osteol. of Mammalia,’ fig. 65, 
p. 206). 
