28 
SYSTEM OF NATURE. 
but slowly, and moved its fore-legs when disturbed. Its 
body was bent upon the abdomen, its short tail tucked in 
between the hind legs, which were one-third shorter than 
the fore legs, but with the three divisions of the toes now 
distinct. The whole length from the nose to the end of 
the tail, when stretched out, did not exceed 1 inch 2 lines.”* 
In the adult animal u the skin of the abdomen is almost 
always so arranged about the mammae as to form a pouch, 
and in this these imperfect little animals are preserved as in 
a second uterus —C. R. A.—and “ closely connected with 
the pouch and with the generation of the animals of the 
present group are the marsupial bones which so peculiarly 
characterize it. These bones are even more constant than 
the pouch,being found in the Echidna andOrnithorhynchus, 
in which no traces of a pouch have been discovered. They 
are elongated and flattened, widely separated at their dis¬ 
tal extremity, and converge as they approach the pubis, to 
which they are joined.”f These “ marsupial bones, so 
common in the skeletons of reptiles, are limited in the 
mammiferous class to this division, in which alone, from 
the peculiarly brief period of uterine gestation and the 
consequent non-enlargement of the abdomen, their pre¬ 
sence might be expected.” + In the formation of the sex¬ 
ual organs both sexes present a marked difference from 
that observed in the placental series : in this family “ the 
uterus does not open by a single orifice into the extreme 
end of the vagina, but communicates with this canal by 
two lateral tubes resembling handles,” and u the scrotum 
of the male, contrary to what obtains in other quadrupeds, 
* Owen, Phil. Trans, part ii. for 1834. 
f Waterhouse, Mar. 67. J Owen, Phil. Trans. 1834, p. 333. 
