1 882.] in the Pectoral and Pelvic Limbs of Birds. 893 



after its true homology has been decided upon. In manus we 

 have quite a number of bones, but we must recollect that the list 

 here given does not occur in all birds. Immature birds, at vari- 

 ous ages, present us with three free metacarpals; these are pretty- 

 generally, at present, taken to be the first or pollex metacarpal, 

 second or index, and third or middle. All three of these bones 

 anchylose together, and with certain carpals, as mentioned above, 

 to form in the adult the bone usually known as the metacarpal, a 

 far better name for which would be the carpo-metacarpal. 



Now pollex metacarpal may support one phalanx, or one pha- 

 lanx and a claw, which may be covered with the common integu- 

 ment, or pierce it and be sheathed with horn. Index metacarpal 

 may possess as many as three phalanges, the last or distal one ex- 

 hibiting the same conditions as the distal joint of pollex ; finally 

 middle metacarpal supports a single phalanx. 



To recapitulate then, we have those adult birds that possess the 

 fewest number of bones in the pectoral limb, presenting us 

 with a humerus, an ulna and radius, two free carpals, a metacar- 

 pal and four phalanges, ten in all, but the complete list of the 

 bones of the avian pectoral limb, up to the present time, are just 

 double this number, though we do not know a single bird that 

 can boast of having them all, either adult or young. 



The following is the complete list : 



~ ' Other bones of the carpus = 3 = os magnum, unciform and pentosteon. 

 = ( Metacarpal = 3 = fast, second and third. 



ii I Phalanges = 6 = 2 for pollex, 3 for index and 1 for 



_ [middle. 



Total 20 



Very many more bones are found in the pelvic extremity of 

 birds than we have just enumerated for the anterior limb, but as 

 already remarked, probably no single bird, either adult or young, 

 possesses them all. 



The limb now under consideration is divided into thigh, leg, 

 tarsus, metatarsus and toes. 



To the thigh is allotted one bone, the femur, while on the other 

 hand the leg or the next division below, has two principal long 

 bones, a heavy one constituting the main support, the tibia, and 



