igos .] ANATOMY OF PHAL/ENOPTILUS, RIDGWAY. 231 



23. M. abductor pollicis (Ab. />/., PL V, Figs. 20, 24). This 

 rather round muscle arises tendinously from the lower surface of 

 the tendon of the m. extensor metacarpi ulnaris (radialis?) some- 

 what proximal to its point of insertion. The muscle then twists 

 around the base of the pollex digit to its ventral surface, and ter- 

 minates tendinously about its mid-point. 



24. M. extensor pollicis brevis is not present. 



25. M. adductor pollicis {Ad. pi, PI. V, Figs. 20, 24). This 

 fairly well developed muscle lies between the posterior surface of 

 the pollex digit and the anterior surface of the third metacarpal. 

 It arises by a strong, fleshy base from the proximal eighth of the 

 third metacarpal, thence it goes obliquely to the pollex digit and 

 is attached by a delicate tendon about one third the length of the 

 digit from its distal end. 



26. M. flexor digiti III (F. dig. Ill, PI. V, Figs. 20, 24). This 

 slender muscle has its origin on the posterior proximal third of the 

 fourth metacarpal. At its fleshy base is a broad ligament extending 

 from the anterior rim of the os ulnare to this point. Near the 

 distal end of this metacarpal the muscle becomes tendinous and 

 finds attachment about the mid-point of the first phalanx of fourth 

 digit. 



Below are given some muscles found on this bird and not men- 

 tioned by Gadow (/. c. ). 



A. {A., PI. V, Fig. 21.) This is a very delicate muscle extend- 

 ing along the dorsal surface of the third metacarpal, and at its origin 

 is covered by tendons of other muscles, fascia and surrounding mem- 

 branes. It arises by a delicate tendon from the distal dorsal edge 

 of the radius. The round fusiform carneous portion is covered by 

 the tendons of the extensor digitorum communis and extensor in- 

 dicis longus. Its distal hair-like tendon fuses with the m. extensor 

 indicis longus at a point opposite the middle of the third metacarpal. 



B. (B., PI. V, Fig. 24.) This slender muscle extends from the 

 distal end of the first phalanx of the third digit to the distal end 

 on the dorsal side of last phalanx of that digit. 



C. From the dorsal distal end of the ulna a tendon passes to the 

 quills. It is not shown in the figures. 



D. (B>. , PL V, Fig. 21.) This is a flat muscle which has its car- 

 neous origin on the proximal dorsal surface of the third metacarpal. 

 It lies between the proximal projection of that bone and the 



