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length of the bodies of the vertebrae. In Hypsiprymnus ur sinus there are more than 

 twenty-six caudal vertebrae. In the Great Kangaroo there are twenty-two caudal 

 vertebrae ; in Bennett's Kangaroo there are twenty-four caudal vertebrae. In Phalan- 

 gista vulpina there are twenty-one caudal vertebrae. Petaurus macrurus has twenty- 

 eight caudal vertebrae ; Pet. taguanoides twenty-nine, while in the Pet. sciureus there 

 are but twenty. In both these species the bodies of the middle caudal vertebrae are 

 remarkably long and slender. Dasyurus maugcei has twenty caudal vertebrae. 



In most of the Marsupials which have a long tail this appendage is subject to pressure 

 on some part of the under surface. In the Kangaroos this must obviously take place 

 to a considerable degree when the tail is used as a fifth extremity to aid in supporting 

 or propelling the body. In the Potoroos and Bandicoots the tail also transmits to the 

 ground part of the superincumbent pressure of the body by its under surface when the 

 animal is erect ; but it is not used in locomotion as a crutch, as in the Kangaroos. In 

 the Phalangers and Opossums the tail is prehensile, and the vessels situated at the 

 under surface are liable to compression when the animal hangs suspended by the tail- 

 To protect these vessels, therefore, as well as to afford additional attachment to the 

 muscles which execute the various movements for which the tail is adapted in the 

 above-mentioned Marsupialia, V-shaped bones, or haemal arches (haemapophyses) are 

 developed, of various forms and sizes, and are placed opposite the articulations of the 

 vertebrae. The haemapophyses embrace and defend the blood-vessels ; and the haemal 

 spine, continued from their point of union, presents a variety of forms in different 

 genera for the attachment of muscles. 



Of the thoracic ribs, which, with the exception of the Tasmauian Wombat, Koala, 

 and Petaurists, are thirteen pairs, the first is the shortest, and, except in some of the 

 Petaurists, the broadest. In the Pet. macrurus the fifth, sixth, or seventh are the 

 broadest ; and the ribs generally have, both in this species and in Pet. sciureus, a more 

 compressed form than in the other Marsupials ; but this character does not exist in 

 Petaurus taguanoides. In the Kangaroos they are very slender and rounded, except at 

 the sternal extremities, which are flattened for the attachment of the cartilages : the 

 seven anterior pairs of ribs articulate directly with the sternum. The cartilages of the 

 six false pairs are long and bent towards the sternum, but do not join it; nor are they 

 confluent, but have a gliding motion one over the other. In the Petaurists six pairs 

 out of the twelve, and in the Tasmanian Wombat six pairs only out of the fifteen, reach 

 the sternum. 



The sternum consists of a succession of elongated bones, generally six in number. 

 The first bone, or manubrium sterni, is the largest, and presents in many species a 

 , triangular shape (from the expansion of its anterior part), and sometimes a rhomboidal 

 figure. A strong keel or longitudinal process is given off in some species from the 

 middle of its haemal or outer surface ; the side next the cavity of the chest is smooth 

 and slightly concave. In the Wombats, Phalangers, and others the keel is produced 

 anteriorly into a strong process, against the sides of which the clavicles abut. The 



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