ORDER MARSUPIALIA. 



MARSUPIALS. 



The Marsupials, or so-called Pouched Mammals, comprise a large 

 number of curious animals, including the Kangaroos, Wombats, etc., and 

 are mostly confined to the Australian region. They are represented, 

 however, in the new world by the Opossums (Didelphiida), a number of 

 species of which are found in North and South America; and also in the 

 latter country by Caenolestes,* a representative of the, until lately, 

 supposed extinct family Epanorthidce. 



As the name marsupial implies, in many cases the female is furnished 

 with an external abdominal pouch in which the young, which are born in 

 a very incomplete stage of development,! are placed by the mother 

 and suckled until they are sufficiently grown to be able to move about by 

 themselves. In Phascologale, however, the pouch is only present in 

 rudiment, and it is apparently entirely absent in Myrmecobius. In the 

 American members of the order the pouch is often absent, sometimes 

 rudimentary, and occasionally well developed 



Some Marsupials are herbivorous, others insectivorous, and a few are 

 carnivorous. The North American Opossums seem to be practically 

 omnivorous. Members of the family are terrestrial, arboreal or bur- 

 rowing, and one (Chironectes), a small Central and South American 

 species, has webbed hind feet and is semiaquatic. 



Among members of this order usually only one tooth of the milk set 

 is functional, the fourth premolar; a developed clavicle is always present. 

 There are differences in brain characters which distinguish Marsupials 

 from higher mammals, among which is the. almost total absence of a true 

 corpus callosum. The cloaca is reduced and shallow. A true allantoic 

 placenta is rarely present (so far as known, only in Parameles). The 

 uterus and vagina are double. The mammae vary in number but .are 



* A number of specimens of this little known Marsupial were taken by Mr. W. H. 

 Osgood in the mountains of western Venezuela and eastern Colombia in the spring of 

 1911. Study of this material is now under way and will be the subject of a special 

 paper which will appear later in the Publications of this Museum. 



t Flower and Lydekker say, "In this stage of their existence they are fed by 

 milk injected into their stomach by the contraction of the muscles covering the 

 mammary gland, the respiratory organs being modified temporarily, much as they 

 are permanently in the Cetacea, the elongated upper part of the larynx projecting 

 into the posterior nares, and so maintaining a free communication between the lungs 

 and the external surface independently of the mouth and gullet, thus averting the 

 danger of suffocation while the milk is passing down the latter passage." (Mammals 

 Living and Extinct, 1891, pp. 130-131.) 



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