18 



Suborder V. ACCIPITRES. 



DesmoguatLous birds •with curved claws, having, except iu Ser- 

 pentavius, the log shorter than the wing ; the rostrum is hooked, the 

 angle of the mandible not recurved, and, except in Pandion, the 

 fourth digit of the pes not reversible. 



The tarso-metatarsus is shorter than the tibio-tarsus, and, except 

 in Pandion ', Serpentariiis, and Catliartidce, presents the following 

 distinctive characters. It is usuallj- more or less short, compressed 

 from back to front, with a distinct ridge on the outer border of the 

 anterior surface, and a sharp inner border, the section of the shaft 

 being more or less triangular ; the proximal surface is transversely 

 elongated, with the talon forming two prominent crests, separated 

 by a very wide groove ; the distal trochlea; are placed more or less 

 nearly on the same level, their plane forming a slight and regular 

 curve. The terminal phalangeals form curved claws, the hallux 

 being of very large size. 



The tibio-tarsus always has an obliquely-placed bridge over the 

 groove for the extensor tendons, which is devoid of a tubercle (fig. 7). 

 With the above-mentioned exceptions ", the following characters 

 are distinctive. The fibula is attached by one ridge below the head 

 and by a second above the distal extremity ; the cnemial crest is 

 small ; the shaft is flattened from back to front, with a slight groove 

 on the distal part of the anterior surface ; the distal articular ex- 

 tremity is much expanded transversely, with a very wide and shal- 

 low intercondylar space, and the posterior trochlear surface very 

 sliallow, and occupying the whole width of the bone. 



The femur is stout, with a large pneumatic foramen on the upper 

 part of the anterior surface at the trochanteric border : the tuberosity 

 is higher than the head ; the fossa for the ligamentum teres is well- 

 developed ; the anterior trochlear groove is deep, nearly vertical, 

 and inclined greatly towards the posterior aspect ; while the external 

 condyle is very prominent, and not much lower than the internal 

 one. 



The furcula is U-shaped, with the rami very divergent at their 



' Iu this genus the fourth digit is reversible, the depression for the extensor 

 hallueis on the anterior surface of the proximal extremity of the tarso-metatarsus 

 has a bony bridge, and the distal trochlear of the same bone resemble those of 

 the Striges. 



^ The tibio-tarsus of Pandion resembles that of the Striges in the depth of 

 the inter-condylar space, both anteriorly and distally, and also in the depth of 

 the extensor channel. 



