iMARSUPIALIA rOUCH 



12 



ou tlie whole in the Polyprotodont forms, such as the Thylacine, 

 ] );tsyures, etc., but is found in so many of them that the 

 two divisions of the Marsupials, the Diprotodonts and the Poly- 

 protodonts, cannot be raised to distinct orders on this and other 

 ^rounds. The marsupial pouch of the Marsupials must not, as 

 has been already pointed out, be confounded with the pouch of the 



Fio. 59. — Rock Wallaby {Petrogale xaidhopus), with young in pouch. x f . 

 (After Vog't and Speclit. 1 



Monotreme mammals. Distinct teats are found in the marsupium 

 of tlie Marsupials, while there are none in the mammary poucli of 

 the Monotreme, the pouch itself indeed representing an un- 

 differentiated teat, of which the walls have not closed up. The 

 pouch opens forward in the Kangaroos, and backwards in the 

 Phalangers and in the I'olyprotodonts. Its walls are supported by 

 a pair of bones diverging from each other in a V-shaped manner ; 

 these are cartilaginous and vestigial in the Thylacine. They 



