THE SKELETON IN MAMMALIA. THE MANUS. 511 



developed digits and large carpal bones. The carpals however 

 interlock to a slight extent, and the corner of the magnum 

 reaches the scaphoid. 



In the PROBOSCIDEA the manus is very short and broad, with 

 large somewhat cubical carpals which articulate by very flat 

 surfaces and do not interlock at all. .All five digits are present, 

 and none of them are much reduced in size. The manus in 

 Proboscidea and in Coryphodon is subplantigrade. 



In the Tillodontia the manus is plantigrade and has pointed 

 ungual phalanges, in this respect approaching the Carnivora. 

 It differs however from that of all living Carnivora in having 

 the scaphoid and lunar distinct. 



In RODENTIA the manus nearly always has five digits with 

 the normal number of phalanges : the pollex may however be 

 very small as in the Rabbit, or absent as sometimes in the 

 Capybara. The scaphoid and lunar are generally united, and 

 a centrale may be present or absent. In Pedetes coffer the 

 radial sesamoid is double and the distal bone bears a nail-like 

 horny covering. In Bathyergus the pisiform is double. It is 

 upon these facts that the contention for the former existence 

 of prehallux and post-minimus digits has partly been based. 



In living CARNIVORA the scaphoid, lunar and centrale are 

 always united, forming a single bone. All five digits are 

 present, but as a rule in Carnivora vera the pollex is small, and in 

 Hyaena is represented only by a small metacarpal. Sometimes, 

 as in Cats and Dogs, the manus is digitigrade, sometimes, as in 

 Bears, plantigrade. The ungual phalanges are large and point- 

 ed, and in forms like the Cats, whose claws are retractile, they 

 can be folded back into a deep hollow on the ulnar side of the 

 middle phalanx ; a small radial sesamoid is often present. 



In Pinniped ia the manus is large and flat and the digits 

 are terminated by ungual phalanges which are blunt (sea lions 

 and walrus), or slightly curved and pointed (seals). The pollex 

 is nearly or quite as long as the second digit, and as a rule 

 the digits then successively diminish in size. 



