ORDER CARNASSIER. 17 



similarly modified as in the monodelphes, as also is the 

 articulation of the cranium. Nevertheless, in the two ano- 

 malous species of this group, the holes through which the 

 nerves of the spinal marrow pass are pierced in the middle 

 of the body of each vertebra, pretty nearly as in Birds, and 

 the ribs articulate only with the body of the vertebrae, and 

 not with the transverse apophyses. 



The limbs have many characters common to all the 

 animals of this group, and some altogether peculiar. 



Thus, in the fore-limbs, are constantly complete clavicles, 

 which are remarkable from the manner in which they are 

 articulated with the anterior piece of the sternum, and in 

 the mode of their junction with the acromion. In the ano- 

 malous species, they offer a disposition still more singular 

 by the manner in which they are, as it were, doubled by 

 certain lateral appendages from the first piece of the 

 sternum. The shoulder-blade has then always an acromion 

 apophysis tolerably developed, but no coracoid. 



A constant character of the humerus is that its internal 

 condyle is pierced by a hole for the passage of the median 

 nerve ; a disposition not unfrequently to be found in other 

 Mammalia, but which is invariable in the Marsupiata. 



Though the fore-paw, or hand, be subject to vary, there 

 are never less than four fingers with the rudiment of a 

 thumb. In general, the humero-cubito-radial articulation 

 is tolerably perfect. 



In the hinder limbs three principal and essentially cha- 

 racteristic points are to be remarked. The first, and most 

 remarkable is, the presence of a particular bone, found in 

 no other mammiferous animal even in a rudimental state. 

 This is usually named the os marswpiale, or janitor marsupii, 

 because it is considered as the bone which opens or closes 

 the pouch. This is, however, by no means universally 

 true ; for many species, and among others the whole group 



Vol. III. C 



