220 THE MYOLOGY OF THE EAVEN. 



one I have last described seems to correspond to tliis 

 writer's extensor pollicis hrevis, but liis description is 

 not very definite. 



I dissected four pairs of feet of this species, — and 

 the dissection is by no means an easy one, — before I 

 was satisfied tliat the facts in regard to these short 

 extensors of the toes are as I have given them above. 

 They were the same in all, and in all the extensor 

 hrevis digitorum of Owen w^as absent. 



Professor Mivart, in his Eletnentary Anatomy, does not 

 mention the short extensor of the hallux as occurring 

 in birds, and this eminent biologist calls this muscle 

 the extensor proprius haUucis. 



In certain birds with zygodactyle feet, as in Geoeoccyx 

 for instance, the morphology of the extensor hallucis 

 hrevis is quite different, and when treating the myology 

 of G. californianus it led me to consider the present 

 muscle as only a part of the extensor hrevis digitorum 

 in that form, and I said in effect that the extensor hrevis 

 digitorum is a muscle that may be taken as an ampli- 

 fication of the muscle I have described in the Eaven as 

 the extensor hcdlueis hrevis. 



But even here in Geoeoccyx the short extensor of the 

 hallux has a certain amount of individualization, thousfh 

 it is not fully differentiated from the other part of this 

 extensor hrevis (Fig. 64 his). It, however, is not at- 

 tached more than half-way down the anterior aspect of 

 the shaft of the tarso-metatarsus, at which point it 

 terminates in a delicate thread-like tendon ; this passes 

 directly over the upper border of the accessory meta- 

 tarsal, and along the top of the basal joint of the hallux, 

 to become inserted in the usual manner in the base 

 of the claw-joint. Now the remainder of the extensor 

 hrevis digitorum is attached down the shaft of the tarso- 

 metatarsus, as far as the distal trochlese ; the outer 



