xvi.] CARNIVORA. 287 



The metacarpals and phalanges are of the complete and 

 normal number in all, with the following exceptions. In the 

 African genus of Long-tailed Monkeys (Celobus), and also in 

 the American Spider Monkeys (A teles], the thumb is rudi- 

 mentary, having usually but one very minute phalanx, in 

 addition to the metacarpal. In the Potto (Perodicticus) and 

 some allied Leuiitrince, the second (or index) digit is very 

 much shorter than the others, and has but two rudimentary 

 phalanges. 



The phalanges are generally more curved than in Man, 

 most notably so in the Orang. The hand of the Mada- 

 gascar Aye-Aye (Chiromys) is remarkable for the extreme 

 attenuation of the bones of the third digit. 



tcl 



FIG. 93. Bones of the carpus of a Bear (Ursus americanus), 5. si scapho-iunar 

 bone ; t cuneiform ; p pisiform ; unciform ; in magnum ; td trapezoid ; tin tra- 

 pezium ; rs radial sesamoid ; i v the metacarpals. 



In the CARNIVORA, the scaphoid and lunar bones always 

 coalesce into a single scapho-lunar bone (Fig. 93, st), with 

 which the centrale is united, the latter never appearing x as 

 a distinct bone, except sometimes in very young animals. 

 The radial accessory ossicle or sesamoid (rs) is generally 

 present. All have five digits, with the complete complement 

 of phalanges, except the Hyaena, in which genus the pollex 



1 See B. G. Wilder, " On the Composition of the Carpus in Dogs." 

 Bull. Cornell University, vol. i. p. 301, 1874. 



