38 GENERAL ANATOMICAL CHARACTERS 
inner and under surface is frequently dilated into a shell-like 
auditory bulla (Fig. 8). The small bones of the internal ear known 
as the malleus, incus, and stapes are contained in the membranous 
tympanic cavity, 
which is situated in 
a space left among 
this group of bones. 
Further mention of 
these bones is made 
below under the 
head of the sense 
organs. 
In the Carni- 
vora and some other 
groups the foram- 
ina on the base of 
the skull for the 
passage of blood- 
vessels and nerves 
are of considerable 
taxonomic import- 
ance. The position 
of the more im- 
portant of these 
foramina is indi- 
cated in Fig. 8; 
but for details the 
reader may refer to 
the work on the 
Osteology of the Main- 
malia already men- 
tioned. Attention 
Fic. 8.—The right half of the hinder part of the base of the 
cranium of the Wolf (Canis lupus). ¢, Condyloid foramen ; 1, fora- may, “ however, be 
men lacerum posticum ; car, carotid canal; e, eustachian canal; particularly di- 
o, foramen ovale; a, posterior, and a’, anterior aperture of ali- rected to the s0- 
sphenoid canal; P, paroccipital process of exoccipital ; m, mastoid . 
process of periotic ; am, external auditory meatus; g, glenoid for- called alisphenoid 
amen, below which is the glenoid cavity for the condyle of the man- canal, the position 
dible. (Flower, Proc. Zool. Soc., 1869, p. 25.) of which is shown 
in Fig. 8, since this is a feature of some importance in the classifica- 
tion of the Carnivora. This canal is a short channel running hori- 
zontally forward from near the foramen ovale through the alisphenoid, 
and opening anteriorly with the foramen rotundum ; it is traversed 
by the external carotid artery. 
Only in those species, as Man and the smaller kinds of the 
Primates and some other orders, in which the brain holds a large 
relative proportion to the rest of the body, does the external form 
