VERTEBRATA. 



241 



As no linear arrangement of the Mammalia can be quite satis- 

 factory, an attempt is here made to show the affinities of the 

 orders in a diagrammatic form. No species of Bruta, however, 

 the lowest of the placental Mammalia, and a fragmentary 

 order appears to approximate to any known Marsupial. The 

 passages from the latter to the Eodentia is made by the wombats, 

 and to the Insectivora by the smaller opossums. The affinities 

 of the remainder are not doubtful. 



Bimana. 



Carnivora. 



Pinnipedia. 

 Hyracoidea. 



Proboscidea. 



/ \Sirenia. 



Ungulata. Cetacea. 



Quadrumana. 



Insectivora. 

 Eodentia. 



Bruta. 

 \ 



Marsu 



Chiroptera. 



(ialia. 



Monotremata. 



According to Schmarda there are above 2300 recent and 300 

 extinct species of mammals. 



Order I. MONOTEEMATA. 

 ORNITHODELPHIA. 



A common cloaca. Jaws without true teeth. No marsupial 

 pouch. Mammary gland without a nipple. No corpus callosum. 



The face is prolonged into the form of a bird-like beak, covered 

 by a smooth skin, the mouth at the extremity and without fleshy 

 lips, although they are for a time manifest in the young. 



Another inferior character, like the common cloaca, is that 

 the coracoid bone extends from the scapula to the sternum ; they 

 have also an epicoracoid or interclavicle, and an episternum, as 



R 



