OPISTHOCOMI 



289 



of six knees that he examined the anibiens was present, 

 though small ; but in only one knee did it cross the knee to 

 be inserted in the usual fashion in connection with the flexors 

 of the leg. Mitchell dissected this muscle in two specimens ; 

 in one the ambiens was completely absent above the knee, 

 but in each case (see fig. 63, p. 96) a ligament left the fibula, 

 and, dividing into three, joined each of the three perforated 

 flexors in the way in 

 which, as has been 

 already described, it oc- 

 curs in birds which have 

 this ambiens rudiment. 

 In the second case there 

 was an ambiens above 

 the knee, but it became 

 lost upon the fascia of 

 the knee, and not con- 

 nected with the ambiens 

 rudiment springing from 

 the fibula, which was 

 there present. So in 

 this bird there are many 

 stages in the reduction 

 of this characteristic 

 muscle, which is clearly 

 in them on the wane. 



It is apparently the 

 rule among birds for 

 there to be a vinculum 



between the two superficial flexors of digit III. This slip 

 is wanting in Opisthocomus, as it is, according to Mitchell, 

 in Asio otus and Bhytidiceros plicatus. The deep flexor 

 tendons are connected by .a strong vinculum. 



The syrinx has been' described by Gaerod and myself. 

 The accompanying figure is from Gabrod's paper.. The 

 last few rings of the treichea are solidified into a tracheal box, 

 and the intrinsic muscles .do not reach this box, being only 

 continued on to it by a ligamentous continuation. There is 



XJ 



Fig. 142. — Steinx of Opisthocomus. 

 View. (Afteb Gakkod.) 



Feont 



