MONOTREMATA. MARSUPIALIA. 301 



body, and, as in the Beavers, a flat tail. The jaws, like the beak of 

 a Duck, are adapted for burrowing in mud, but are armed on 

 both sides with two horny teeth, and are surrounded by a horny 

 integument, which, at the base of the beak, projects in a peculiar 

 manner, so as to form a kind of shield. The legs of Ornithorhynchus 

 are short; the five-toed feet end with strong claws, but are also 

 furnished with very extensible webs, and are, therefore, equally well 

 adapted for swimming and burrowing. Both sexes have, like the 

 Marsupials, in front of the pubis the so-called marsupial bones, 

 which in the female Echidna support a pouch. The testes remain 

 inside the body cavity (i.e., do not descend into a scrotum). The 

 males in both the genera possess a hollow spur on the hind foot, 

 which receives the duct of a gland, to which for a long time poisonous 

 properties were erroneously attributed. It appears more probable 

 that this spur serves only as a stimulant during copulation, since it 

 fits into a pit in the thigh of the female. The embryos * are born at 

 an early stage, and in Echidna, pass into the marsupial pouch of the 

 mother. On the abdomen of the latter there are two mammary 

 glands, which are without a projecting nipple. Fossil remains are as 

 yet unknown. 



Ornithorhynclms paradoosus Blumb., The Duck-bill Platypus, Australia and 

 Van Diemen's Land ; Echidna Jiystrix Cur., in the mountainous regions of 

 south-east Australia ; E. setosa Cuv., Van Diemen's Land. 



Order 2. MARSUPiALiA.t 



Mammalia with various dentition, with two marsupial bones sup- 

 porting a marsupial pouch, which encloses the teats of the mammary 



The principal characteristic of the Marsupials is the possession of 

 a sac, or pouch (marsupium), which is supported by two marsupial 

 bones (fig. 683), encloses the teats of the mammary glands, and 

 receives the helpless young after birth. In the absence of a placenta, 

 birth, as in the Moiiotremes, takes place at a very early stage. Even 

 in Macropus giganteus, the males of which attain almost the height 

 of a man, the period of gestation does not last more than thirty-nine 

 days, and the embryo at birth is blind and naked, its extremities are 



* Vide note. p. 296. 



f E. Owen, " Marsupialia," in Todd's Cyclopaedia of Anatomy, vol. in., 1842. 

 G. R. Waterhouse, " A Natural History of the Mammalia," vol. v., " Marsu- 

 pialia," London, 1846. 



