6 MR. W. H. FLOWER ON THE [ Jan. 14, 
utility to the zoologist ; and this will be more especially the case when 
the part in question is one so imperishable, so easy of examination, 
and affording indications so clear and capable of ready definition and 
description, as the base of the skull. 
In order not to extend this communication to too great length, or 
over too great a variety of subjects, I propose to limit my observa- 
tions on the present occasion mainly to the terrestrial or fissipedal 
Carnivora, and only to those genera now existing. My reason for 
this last restriction is, that itis only in these that we have the oppor- 
tunity of thoroughly working out all the important points of struc- 
tural modification throughout the system, and thus definitely assign- 
ing their position; and “from these only can we hope to establish 
any correlation between the structure of the hard and imperishable 
parts and the viscera. When such a correlation has been established, 
then the examination of the fragmentary remains of the extinct forms 
can be made with much greater advantage, and the work of tracing 
the stages by which the present condition of the order has come into 
being can be approached with more probability of a satisfactory 
result. 
The region to which attention will now be especially directed is the 
posterior ‘part of the base of the cranium, the most conspicuous fea- 
ture in which, in all Carnivora, is the auditory bulla ; and it is mainly 
the characters of this bulla, and the structures immediately surround- 
ing it, which will be described in the principal genera of the order. 
Following Mr. Turner’s example, I will first take one of the ex- 
treme forms of existing terrestrial Cariivores, the Bear. 
Figures | and 2 (pp. 7 & 8) are taken from the skull of a not quite 
adult Ursus ferox in the Museum of the Royal College of Surgeons 
(No. 4016). 
The auditory bulla is comparatively little inflated. It consists of 
a single bone, readily detached from the cranium in skulls of young 
animals. Its form is more or less triangular, being broad and nearly 
straight at the inner edge, and prolonged outwards into the much 
produced floor of the external auditory meatus (m.a). Its greatest 
prominence is along the inner border; from this it gradually slopes 
away towards the meatus. Near the hinder part of the inner edge 
is a considerable circular foramen (ear), which pierces the bone 
obliquely, leading to a canal which runs forwards in an arched direc- 
tion, in its inner wall. This is the carotid canal. In old Bears the 
entrance is partly concealed by the prominent lip of the basiocci- 
pital, which abuts against the inner edge of the bulla; and by the 
growth of this and of the paroccipital process it becomes almost in- 
cluded in the deep fossa leading to the foramen lacerum posticum (/). 
Anteriorly the carotid canal of the bulla ends close to the inner side 
of the groove for the eustachian tube; and the artery quitting it 
takes a sudden turn upwards and backwards and enters the cranium 
through the foramen lacerum medium. 
When a section is made through the auditory bulla (see fig. 2, p. 8) 
it is seen to be a simple thin-walled bony capsule, imperfect above, 
where it fits on to the petrosal and squamosal bones, and prolonged 
