68 INTRODUCTION. 



sexes of the Marsupial animals, are relatively longest, 

 straightest, and most slender in the Perameles ; 

 flattest, broadest, and most curved in the Koala, 

 sometimes, as in the Womhat, they are articulated 

 to the puhis, by two points. They are always so 

 long, that the cremaster muscle winds round them.* 

 In the various memoirs on the anatomy of the 

 Marsupialia, published by Professor Owen, who has 

 particularly devoted his attention to the study of these 

 animals, he has constantly found it necessary, in his 

 comparisons, to refer to the oviparous classes of 

 vertebrata. " Both sexes in the Marsupial genera/' 

 says this author, " manifest their affinity to the 

 oviparous classes, in possessing two superior vence 

 cavce, and in the want of the inferior mesenteric 

 artery : and the Marsupial bones, so common in the 

 skeletons of reptiles, are limited in the mammiferous 

 class to this division, in which alone, from the 

 peculiarly brief period of uterine gestation, and the 

 eonsequent non-enlargement of the abdomen, their 

 presence might be expected. But these bones serve 

 important purposes, in relation to the generative 

 economy of the Marsupiata. In the female they 

 assist in producing a compression of the mammary 

 gland, necessary for the alimentation of a peculiarly 

 feeble offspring, and they defend the abdominal viscera 

 from the pressure of the young, as these increase in 

 size, during their mammary or marsupial existence, 



* See Professor Owen's paper On the Osteology of the 

 Marsupialia.^ Proceedings of the Zoological Society for 



