THE SKELETON IN MAMMALIA. THE MANUS. 505 



In the Sloths the manus is very long, narrow, and curved, 

 and terminated by two or three long hooked claws, borne 

 by the second and third, or the second, third and fourth 

 digits. The fifth digit is absent, and the fourth is represented 

 only by a small metacarpal. In the Anteaters the third digit 

 is greatly developed and bears a long hooked claw. In Myr- 

 mecophaga all five digits are fairly well though irregularly 

 developed, in Cydoturus the first, fourth, and fifth, are vesti- 

 gial. In the Armadillos the manus is broad, and has strongly 

 developed ungual phalanges. The digits, though almost always 

 five in number, vary much in their relative arrangement. In 

 Dasypus they are regular, but are remarkably irregular in 

 Priodon. The pollex is absent in Glyptodonts and in Mega- 

 therium. In Megatherium the fifth digit is clawless while the 

 second, third, and fourth bear enormous claws. In the Manidae 

 the scaphoid and lunar are united; five digits are present, 

 the third and fourth being very large, and all being terminated 

 by deeply cleft ungual phalanges. In Orycteropus the pollex is 

 absent, while the other digits are terminated by pointed un- 

 gual phalanges. 



In SIRENIA the general structure of the manus is quite of 

 the ordinary mammalian type. In Manatus most of the bones 

 of the carpus are distinct, but in Halicore many, especially 

 those of the distal row, have coalesced. The digits are always 

 five in number and have the normal number of flattened 

 phalanges. 



In the CETACEA, on the other hand, the manus is much 

 modified by the fact that the number of phalanges may be 

 greatly increased above the normal number of three, thirteen 

 or fourteen sometimes occurring in each digit. These are 

 believed to be duplicated epiphyses. In the Mystacoceti the 

 manus remains largely cartilaginous, in the Odontoceti it is 

 better ossified, and the phalanges commonly have epiphyses at 

 both ends. In Physeter the carpal bones also have epiphyses. 

 The carpus generally consists of six bones arranged in two 



