CANIDA 
545 
A cecum is always present, sometimes short and simple, but when 
long it is folded upon itself in a characteristic manner. 
The characters of the base of the cranium are shown in Fig. 8 
air /. 
we > 
pes 
Ke 
YS 
> 
Fic. 249.—Right lateral aspect of the skull of the Dog (Canis fumiliaris). 
(p. 38), where it will be seen that the auditory bulla is inflated, 
although it has only a rudimental internal septum ; the paroccipital 
process, although in contact with the bulla, is 
prominent, and there is a large glenoid foramen. 
In all the existing forms the humerus has lost the 
entepicondylar foramen; the crowns of the upper 
molars are triangular in shape (Fig. 251), and the 
blade of the upper carnassial consists of two lobes. 
In the alimentary canal the cecum (Fig. 250) is 
extremely characteristic. It is a simple appendage 
of nearly uniform width (about equal to that of the 
ileum) attached to the side of the canal, just beyond 
the ileo-cxecal valve, and with a rounded termination. 
In a Dog of average size it is 5 or 6 inches long if 
uncoiled, but it is normally folded by its mesenteric 
attachments backwards and forwards several times 
on itself by the side of the ileum, after the manner 
shown in the figure. 
The existing Dogs form a very compact group, 
with numerous species closely resembling each other 
in essential characters, though differing considerably 
externally. The most marked differences are slight 
variations in the number of the true molar teeth, 
which exceed the usual number in the Cape Long- 
eared Fox (Otocyon), and fall short of it in some other 
less aberrant forms to which the names of Icticyon 
and Cyon have been given, and a diminution in the 
number of toes in the Cape Hunting Dog (Lycaon), 
Fic. 
Cecum of the Arc- 
tic Fox (Canis lago- 
250. — 
pus). %, Tleum; c, 
colon. In the nat- 
ural position the 
colon is  upper- 
most. 
which has 4-4, instead of 5-4 as in the remainder of the family. 
35 
