1050 DR. p. CHALMERS MITCHELL ON THE 



the shaft. The anchor is always present and is usually rather 

 long and slightly fan-shaped. The slip to III is always present 

 and normal. The P. brevis is very strong ; it arises in the 

 Lammei'geier only from the lower end of the fibula and the tibia 

 distal of this ; in Ictinia its origin begins higher up ; in the 

 others, as shown in text-fig. 182, it arises from nearly the 

 whole length of the fibula below the biceps insertion, from the 

 adjacent surface of the tibia and from the tibia distad of the end 

 of the fibula. Its very strong tendon passes under a fibrous 

 bridge wliich may be calcified in old birds, then flattens out and 

 passes in the usual synovial sheath under the slip to III to its 

 normal insertion. 



It is plain that in these birds-of-prey the superficial origin of 

 the P. longus has been partly or completely lost and that the 

 P. brevis has greatly increased in relative importance, until it 

 may sui-pass the P. longus. 



Pandionidse. Pandion hcdiaetus. — In the Osprey I found no 

 trace of the P. longus, in which I am confirmed by Dr. Gadow. 

 The P. brevis was short and not very strong, arising from the 

 usual origin limited to the lower half of the shaft and passing 

 into a weak tendon, which after traversing a bony bridge, 

 flattened out and had the normal insertion of this muscle. As 

 ornithologists, arguing from other features, have diflfered as to 

 placing the Osprey with the Eagles and Vultures, or with the 

 Owls, it is of some interest to note that in the Owls also only the 

 P. brevis is present. 



Apai't from Pandion, it is clear that the Falconiformes 

 generally show a gradual reduction or specialization of the 

 P. longus, always retaining, however, the deep origin, the anchor 

 and a stiong normal slip to III, and a gradual increase in size of 

 the P. brevis. 



Gadow unites the Oiconiiformes, Anseriformes, a,nd Falconi- 

 formes into the " Legion " Pelai^gomorphpe. Again excepting 

 Pandion, it appears that throughout the Legion, the P. longus 

 remains a large and important muscle always with a good anchor 

 and good slip to III, but that the P. brevis offers every condition 

 from that of perfect equality with or even su2:)eriority to the 

 longus in the specialized Falcons, to complete absence. 



Alsctoromorph^. 



TiNAMIFORMES. 



C r y p t u r i. Rhynchotus rufescens (4 examples). Nothura 

 maculosa. Calodromas elegans(3 examples). — In all the Tinamus 

 I examined, the P. longus was well developed, with very large siiper- 

 flcial and fascial origins and long deep origin. The anchor was 

 strong and broad and the slip to III strong. T noticed that in a 

 Ilvifous Tinamu the P. longus first straightened the tarsal joint a.nd 

 then flexed sharply the second as well as the third digit. On dis- 

 secting out the tendons, I found that the tendon of the perforated 



