xvi.] EDENTATA. 309 



terminate in subequal, compressed, ungual phalanges of 

 moderate size. The second and third digits are nearly 

 equal, the fourth and fifth shorter. A sesamoid bone is 

 developed on the dorsal side of the metacarpal-phalangeal 

 articulations. 



Order MARSUPIALIA. The carpus never has a distinct 

 os centrale. It is commonly stated that there is a scapho- 

 lunar bone ; but the lunar, though always small, is distinct 

 in Didelphys, Perameles, Dasyurus, Thylacinus, Phalangista, 

 and Hypsiprymnus (where it is very minute) ; and its ab- 

 sence in Macropus appears to be due rather to suppression 

 than to coalescence with the scaphoid. In Phascolomys a 

 small lunar is present in some individuals, and not in others. 



With the exception of the genus Chceropus, all known 

 Marsupials possess the normal number of digits and pha- 

 langes, and the manus is short and rather broad, with 

 moderately developed, compressed, curved, ungual pha- 

 langes. 



The little " pig- footed " insectivorous Marsupial, Chotropus 

 castanotis, belonging to the family Peranulida, has a remark- 

 ably modified manus (see Fig. 112) in which only two 

 digits are functionally developed ; and as the metacarpals 

 are very long, and closely pressed together (though not 

 ankylosed), and the phalanges are short, and the nails rather 

 hoof-like, the whole manus has much general resemblance 

 to that of the Artiodactyle Ungulates. It presents, how- 

 ever, the essential difference that the functional digits are 

 the second and third of the normal series, instead of the 

 third and fourth. This is proved by comparing it with 

 the less modified manus of a true Perameles (Fig. in). 

 The principal changes from the typical Mammalian manus 

 observed in Perameles are the great reduction of the 

 first and fifth digits; while the second, third, and fourth 



