MAMMALIAN ORDERS. 



275 



151 



uterine ovum, dissected, Ornitho- 

 rliynclius. Lxxvir. 



true ^testlconda/ and are ovoviviparous, fig. 151: they have a 

 coracoid bone extending from the scapula to the sternum, and 

 also an epicoracoid and episternum, as 

 in Lizards ; they are unguiculate and 

 pentadactyle,^ with a supplementary 

 tarsal bone supporting a perforated spur 

 in the male. The order so character- 

 ised is called * Monotremata/ in refer- 

 ence to the single excretory and gene- 

 rative outlet, which, however, is not 

 peculiar to them among Mammalia. The 

 Monotremes are insectivorous, and are 

 limited to Australia and Tasmania ; 

 where they are represented by the Pla- 

 typus or Duck-Mole ( Orjiithorhynchus), 

 and by the Spiny Anteater (^Echidna). 



The Marsupialia are Mammals distinguished by a peculiar 

 pouch or duplicature of the abdominal integument, which in the 

 males is everted, forming a i^endulous bag 

 containing the testes, and in the females is 

 inverted, forming a hidden pouch containing 

 the nipples and usually sheltering the young 

 for a certain period after their birth : they 

 have the marsupial bones, fig. 152, m, in 

 common with the Monotremes ; a much-varied 

 dentition, especially as regards the number of 

 incisors, but usually including four true mo- 

 lars ; and never more than three premolars : the 

 angle of the lower jaw is more or less inverted. 



With the exception of one genus, DidelpJiys, 

 which is American, all the known existing 

 Marsupials are Melanesian, i. e. belong to 

 Australia, Tasmania, New Guinea, and some 

 adjacent isles. The grazing and browsing 

 Kangaroos are rarely seen abroad in full day- 

 light, save in dark rainy weather, 

 the Marsupialia are nocturnal. Zoological 

 wanderers in Australia, Aiewing its plains and scanning its scrubs 

 by broad daylight, are struck by the seeming absence of mam- 

 malian life ; but during the brief twilight and dawn, or by the 

 light of the moon, numerous forms are seen to emerge from tlieir 

 hiding-places and illustrate the variety of marsupial life Avith 

 which many parts of the continent abound. We may associate 



r 2 



Most of ^^"-'^^''^ ^^^^ marsupial boues, 

 Kangaroo. Lxxv. 



