70 
SYSTEM OF NATURE, 
AYES, 
PISCES CART. MARSUPIALIA. 
PLACENTALIA, 
PISCES OSSEI. CATAPHRACTA. REPTILIA 
I will now endeavour to explain my reasons for sup¬ 
posing the placentals thus surrounded, and for this purpose 
I must return to the tribes of placentals as indicated at 
pages 34 and 45, and recapitulate the characters already 
proposed. 
1st. Saltantia. With regard to the character by which 
I have characterized the Glires of Linneus a little expla¬ 
nation appears requisite. I must not be understood as 
asserting that the entire group is remarkable for its leaping 
powers or propensities, but rather that the general struc¬ 
ture indicates an aptitude for such power or propensity, and 
is such that leaping may be always accomplished with 
ease, that being, generally speaking, the mode of progres¬ 
sion adopted by choice. The planta, or sole of the hind 
leg is long, and its entire inferior surface is appressed to 
the ground: when the animal moves forward, the heels 
are raised simultaneously. Like the galloping of a horse, 
its progressive motion is a series of leaps. The rabbit, 
hare, rat, mouse, squirrel, &c., always gallop if forced into 
a quick pace ; they have no choice of rapid progression ; 
they have no walk or trot, like that of a horse,’ an ox, or a 
