OSTEOLOGY OF BIRDS 



93 



upward, with its manubrium long and pointed, and its coracoidal 

 grooves do not decussate. 



Six or seven haemapophyses may reach a costal border in either 

 genus — very rarely only six in Circus. 



The long bones in the limbs in the skeleton of an Accipiter agree 

 very closely with the corresponding (bones in C i r c hi s h u d - 

 s o n i u s [text fig. 29-35 > P L 8, fig. 15, 16]. Also the composition 

 of the skeleton of manus is quite similar, but in the digits of pes 

 some very few good differential characters are seen in these two 

 forms. The relative lengths of the phalangeal joints of the second 

 toe are the same, but in the case of the third toe (middle anterior 

 one) in Circus the phalanx next beyond the basal one is shortened, 

 so that it measures just about half the length of the aforesaid basal 

 one. This is not the case in an Accipiter where the joints of the 

 middle toe progressively become but slightly shorter as we proceed 

 toward the ungual one. These and other differences in these podal 

 joints can best be shown by a brief table of measurements. 



TABLE 



Measurements in centimeters and fractions; the ungual joints not con- 

 sidered; the basal joint is the first measurement, and the others follow in 

 order. 



SPECIES 



Circus hudsonius 

 Accipiter velox . . 

 Accipiter cooperi 



2D TOE 

 BASAL JOINT 



3D TOE 



1.6 



1 . 2 

 J -7 



4TH TOE 



1.6: . 9 : 1.4 .8: .5: . 5 : 1.2 

 1.4: 1.2: 1 . o .6: .4: .4: .9 

 1.9: 1.3: 1.4 j . 9 : . 5 : . 6 : 1 . 1 



The character to which reference has just been made as to the 

 lengths of the phalangeal joints of pes are best seen in the third 

 toe of Circus hudsonius and Accipiter velox, 

 although it shows pretty well in Accipiter cooperi — the 

 variations are similar. The proportionate lengths of the phalangeal 

 joints of the third toe as seen in Circus h u d soni u s are again 

 repeated in the foot of E 1 a 11 u s leucur-us, but in this kite, as 

 has already been pointed out above, the proportionate lengths of the 

 joints of the fourth toe are again very different, or at least the two 

 •beyond the basal one are reduced to their minimum lengths. 



Representatives of the genus Buteo seem to vary but little among 

 the species in so far as the characters of their skeletons are con- 



