VOL. LXXXV.] PHILOSOPHICAL TRANSACTIONS. 541 



these bones, and unite in tlie middle between them. The mammae are covered 

 anteriorly by the lining of the false belly, and the nipples project into that 

 cavity; this covering is similar to the external skin, having a cuticle, and short 

 hair thinly scattered over its surface, except at the root of the nipples, where 

 there are tufts of some length, one at the basis of each. The mammae are 

 supplied with blood from the epigastric arteries. The mammary branches run 

 superficially under the false belly till they reach the mammas. There is a strong 

 muscle that comes down from the upper part of the abdominal muscles, and 

 adheres firmly to each of the mammae; this muscle, when the young is sucking, 

 will prevent the mamma being dragged from its natural situation. 



The 2 bones which lie behind the mammae deserve a particular description, as 

 they are peculiar to the opossum tribe, and belong to the mammae, and false 

 belly, having no other apparent use but what is connected with the motion of 

 these parts. They are about 2i inches long, are flattened, and at their broadest 

 part measure nearly 4 an inch ; they are attached to a projecting part of the os 

 pubis, fitted for that purpose, just before the insertion of the recti abdominis 

 muscles; this attachment to the pubis is by a very small surface, and admits of 

 considerable motion; they have also a connection by a ligament 4- an inch in 

 breadth, to the ramus of the pubis, which joins the ilium. From their base, 

 which is united to the pubis in these ditFerent ways, they become narrower, till 

 they terminate in a blunted point. These bones have a pair of muscles inserted 

 into their base, to bring them downwards and outwards; another pair into their 

 blunted extremities to bring them forwards; a pair of broad flat muscles fill up 

 the whole space between them, arising from their inner edge through its whole 

 length; they serve as a sling to support the mammae, and also to bring the bones 

 towards each other. Besides these additional bones, and the projection to which 

 they are attached, there is another peculiarity in the structure of the pelvis of 

 the female kanguroo; the 1 rami of the os ischium which join the pubis, have 

 no notch between them as in other quadrupeds, but form a rounded convex sur- 

 face of some breadth, projecting considerably forwards; the surface itself is 

 smooth, like those over which tendons sometimes pass; but the lateral parts are 

 rough, and have a pair of muscles arising from them inserted into the skin of 

 the false belly, to bring its moijth towards the pudendum. 



The mode in which the young kanguroo passes from the uterus into the false 

 belly has been matter of much speculation, and it has been even supposed that 

 there was an internal communication between these cavities; but after the most 

 diligent search, I think I may venture to assert that there is no such passage. 

 This idea took its rise from there being no visible opening between the uterus and 

 vagina in the unimpregnated state; but such an opening being very apparent, 

 both during pregnancy and after parturition, overturns this hypothesis; for we 



