IIG MAMMALIAN DESCENT. [Lkct. IV. 



Avorthy of mention. It is not until we are some good lieiglit in the 

 mammalian scale, that we find the mechanism of the ear perfected by 

 what is called a stajjes, or stirrup-bone, in the middle-ear, fitting on 

 to the vestibule of the inner or essential ear. The oviparous tribes 

 which have that peculiar operculum or covering to the oval openmg 

 of the vestibule (fenestra ovalis), namely. Amphibia, Reptiles, and 

 Birds, nearly always have it stalked, so that it forms a little column 

 (columella), with a dilated upper or imier end. The Prototheria, and 

 several of the Metatheria, have this columella instead of the stapes or 

 stirrup-shaped element in the middle-ear ; in the Edentata the 

 Armadillos and the Aard-vark have a stapes ; the Sloths, whilst in 

 their embryonic state, the Ant-eaters, and the Pangolins, have a 

 columella. Thus, in this transitional condition between the oviparous 

 and nobler mammalian tribes, the Edentata and the Marsupials are 

 about on an equality. And this is true all round ; for in some things 

 the latter have the pre-eminence, whilst in others the Edentata are 

 manifestly superior to the Opossums, Phalangers, and Kangaroos. 

 If the New World and the Old World Edentata ever had common 

 parents, a considerable anioinit of time must have elapsed since, to 

 give them the chance of becoming so very distinct as we now find 

 them. If the long-tongued ant-eating Woodpecker is a kind of side 

 branch from the primary Passerine stock, and the long-tongued 

 insectivorous Chameleon is a sort of side-branch of the Lizard stock, 

 then we majr expect curious things to take place in a mammal also, 

 which loses all his teeth through taking to live on Ants. I 

 am arguing as my esteemed colleague Professor Flower argues, 

 and we are of one mind on this matter. I am also in agreement 

 with him when I incline to }»ut the Aard-vark a good Avay off from 

 the rest of the Order ; it comes nearer the Insectivora than anj' 

 other member of the group, whilst the Pangolin refuses to acknow- 

 ledge more than general relationship with the forms from the New 

 Tropics. 



Yet the Pangolin has an equal right with them to l)e considered a 

 descendant of some prototherian beast — some common ancestor to 

 him, to the Neotropical forms, to the Duck-billed Platypus, and to 

 the ant-eating spiny Echidna. 



All the better sort of Mammalia have a plate of bone diwe-tailed 

 in between the great skull-ljones (parictals) and the back wall of the 



