264 THE MAN US. [chap. 



distinct. A distinct os centrale is found in all except in 

 Galeopithecus, Potamogale, Chrysochloris, and Sorex. 



There are nearly always five digits, but Rhynchocyon and 

 Chrysochloris have but four. The whole hand is generally of 

 moderate size, with pointed, conical, slightly curved, ungual 

 phalanges. 



In common with every segment of the anterior extremity* 

 the manus of the Mole (Ta/pa) and its immediate allies is 

 extremely modified to suit its fossorial habits (see Fig 90). 

 It is extremely broad and strong, its breadth being increased 

 by the great development of the radial sesamoid (rs), which, 

 being sickle-shaped, has received the special name of os 

 falciforme. The ungual phalanges are very large, and cleft 

 at their extremities. 



In the Chiroptera, the hand is especially modified in a 

 totally different manner, constituting the organ of flight. 



!In the carpus the scaphoid and lunar are united, and in 

 some genera (as Pteropus) the cuneiform is joined with them, 

 so that the proximal row contains but a single bone. There 

 (is no centrale. The pisiform is very small. 



The pollex is short, divaricated from the other digits, not 

 enveloped as they are, in a cutaneous expansion, and armed 

 with a curved claw. The other digits are extremely long and 

 slender. 



In the Frugivorous Bats {Pteropus) the second digit has a 

 short ungual phalanx and claw, but in each of the other 

 digits the middle phalanx is elongated, and gradually tapers 

 to the termination, the ungual phalanx being absent. 



In the Insectivorous Bats, the pollex alone has a claw. 

 and the elongation of the other digits is chiefly due to the 

 metacarpals, the phalanges being small and very slender, 

 and usually only two in number, except in the third digit, 

 which generally has three. 



