318 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1923 



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captivity, and the young animals, in and out of the pouch, are a 

 never-ceasing wonder to visitors. From the time when the young 

 are first noted moving in the pouch, it is about three months, with 

 these large kangaroos, before the little animal first puts his head 

 out of the opening. Then follows a very interesting and amusing 

 few weeks during which the young is in or out of the marsupium at 

 his pleasure ; sometimes with foot or head out in the most grotesque 

 positions. Finally the mother, when the young animal has grown 

 to a considerable size, refuses it further admission to the pouch. 

 These kangaroos sometimes attain a size of over 5 feet for the head 

 and body alone ; the added length of the great tail makes the animal 

 appear much larger. 



Several smaller species of kangaroos are usually kept in the an- 

 telope house. Among the most interesting at the present time are 

 the rufous-bellied wallaby (M. hillardierii) and the brush-tailed 

 rock kangaroo (Petrogale penicillata). The rock kangaroos are at 

 home in rough country rather than in level areas; the tail is less 

 robust than in the other species and is not used as a ground rest 

 when the animal stands erect. 



The phalanger {Trichosurus vvlpecula) is another Australian 

 species, largely nocturnal, and with the habit of playing " 'pos- 

 sum " like its American relative. It is not active in the cages and 

 is rather uninteresting in the zoo. The wombat (Phascolomys 

 mitchelli) is a powerful, heavy-set brute, with large head and only 

 a short stump of a tail. It is a burrowing animal and is said to 

 live in small colonies. This is an Australian species, but a closely 

 related form inhabits Tasmania. 



The Tasmanian devil {Sarcophilus harrisii) is as ugly disposi- 

 tioned a beast as he is displeasing to the eye. Naturally of nocturnal 

 habits he is not often active in the cage. The Virginia opossum 

 {Didelphis virginiana) is likewise of such retiring disposition that 

 he is seldom seen. A small relative, called the murine opossum 

 (Marmosa murina) , is a native of tropical America and occasionally 

 finds its way into the United States as a stowaway in a bunch of 

 bananas. 



BIRDS 



Birds (class Aves) are often defined as " animals with feathers," 

 and this diagnosis answers every purpose for popular use, since all 

 birds have feathers and no other animals possess them. No class 

 of animals has received so much popular attention and few so much 

 scientific study as have the birds. Almost any single locality offers a 

 large list of species, and the variety to be found during the spring 

 and fall migration makes a study of the birds of any vicinity an 

 interesting and exciting occupation. On account of their great 



