MAMMALIA. 555 
but in the mole the fore-limb is shortened, not length- 
ened, as the medium upon which the work is done is 
solid earth, not air. 
The pelvis of the bat is produced backwards and there 
is usually no pelvic symphysis. The hind-limbs are small. 
The fibula is a small splint-like bone down the side of the 
tibia. There are five toes, of which the first is slightly 
_ the smallest: they bear curved claws. 
As in the mole and porpoise, the adap- Fig. 381. — Larera. 
tation has resulted in increase of the VIEW oF THE STER- 
fore-limb and reduction of the hind- NUM or A Fox-BaT 
limb. (Pteropus). 
The stomach of the fox-bat is simple, 
though the pyloric portion is produced 
into a process. 
The mammz of the bat are pec- 
toral and paired. The fecundity is low, 
as is natural when the parent has to 
carry the family about with her, cling- 
ing to her under-surface. Such a 
position of the young may account for 
the pectoral mamme. 
The adaptation of the bat to an 
zrial habit may be summarised as 
follows :—(1) Fore-limbs and four digits 
elongated, supporting “wing mem- 
brane.” (2) Hind-limbs bent back- 
wards and assisting to support ‘“ wing 
membrane” and “‘interfemoral mem- 
brane.” (3) Keeled sternum, connected 
by large clavicle to scapula. (4) Partial 
ankylosis of dorso-lumbar vertebrae. (5) 
Great development of hearing and of 
‘‘motion-sense.” (6) Small fecundity and pectoral mamme.* 
Note discontinuous keel. 
AERIAL ADAPTATION. 
The eerial types are modified from the arboreal, ayshort step only 
intervening between the two. As examples we may instance the flying 
‘squirrels ” and phalangers of Australia (Czscws, Petaurus), the true 
* Probably connected with arboreal habit which preceded that of flight (c/, 
Primates). 
