MARSUPIALIA POUCH 



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on the whole in the Polyprotodont forms, such as the Thylacine, 

 Dasyures, etc., but is found in so many of them that the 

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

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

 grounds. The marsupial pouch of the Marsupials must not, as 

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



Fro. 59. Rock Wallaby (Petrogale xaiithopus), with young in pouch. 

 (After Vogt and Specht.) 



xf. 



Monotreme mammals. Distinct teats are found in the marsupium 

 of the Marsupials, while there are none in the mammary pouch 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 Polyprotodonts. 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 



