96 



STRUCTURE AND CLASSIFICATION OF BIRDS 



ance of this muscle in classification has been much increased 

 by MITCHELL'S interesting paper upon its exact relations 

 to the flexors of the leg in a series of birds. 1 He has shown 

 that in Baharica clirysopelargus the mass of muscle which 

 forms the flexor perforatus arises from three distinct heads ; 

 one of these is, in common with the flexor lorigus hallucis, 

 from the intercondylar notch of the femur; the second is 



i.QLt/7; 2. 



(JftST 



and 



CRUR 



Iff J? 



I 



FLEX. COM 



Fin. 53. LEG MUSCLES OF Opisthocomus (AFTER MITCHELL). 

 II-IV, flexores in-rt'unii i. 



from the outer condyle of the same bone ; the third is from 

 the tendon of the ambiens. This tendon divides into three, 

 one for each of the three divisions of the flexor perforatus. 

 The arrangement will be obvious from the accompanying 

 cut. Apart from slight differences in detail the same 

 arrangement was found to hold good for a few other birds 

 provided with an ambiens. 



1 ' On the Perforated Flexor Muscles in some Birds,' P. Z. S. 1834, p. 495. 



