228 ON THE ANATOMY OF THE JAANAS. 



in M. albinucna and in M. indicus (as I have been able to ascertain by 

 extracting the wing-bones from a skin), the radius presents the form 

 shown in the drawing (fig. 3), being dilated and flattened into a sub- 

 Fig. 3. 



Wing-bones of Metopidius albinucka, to show the peculiarly modifie d radius ; 



natural size. 



triangular lamellar-like expansion for its distal half. Its superior surface 

 is slightly grooved posteriorly for the tendon of the extensor metacarpi 

 radialis longior muscle. 



This dilated portion forms the margin of the patagial space for its 

 distal portion. A considerable portion of the marginal tendon of the 

 tensor patagii longus is inserted into the radius at the angle of the bone ; 

 the main tendon, however, continues in a groove on the inferior aspect 

 of that bone, a little behind the border, to its ordinary insertion. About 

 half of the peculiar flattened radius is left bare of muscle above, the 

 extensor metacarpi, as already stated, playing over its lower half. Below, 

 the flattened area is largely covered by the fibres of the pronator radii 

 superficialis, which extend up nearly to the margin of the bone ; below 

 this is the pronator radii profundus, which likewise has an extensive 

 insertion into the lower part of the bone. The margin of the bone, where 

 it is superficial, is slightly roughened ; and no doubt the peculiar form of 

 radius is associated with the quarrelsome habits of these birds, this dilated 

 and somewhat scimitar-shaped bone being probably capable of inflicting a 

 very severe downward blow. 



In Parrajacana and P. gymnostoma the radius presents the ordinary 

 form ; and the same is the case in Hydrophasianus chirurgus. 



P. Z. S. 1881, In these two genera, it is to be observed, the metacarpal "spur" is 

 much more developed and sharp than in the species of Metopidius, where 

 it is small and blunt ; so that there is a correlation apparently between a 

 sharp spur and a simple radius, and a blunt spur and flattened radius. 

 In Hydralector gallinacea there is a blunt spur, with, so far as I can 

 make out from a skin, a flattened radius. 



The " claw " or " spur " of the wing of the Jaganas has, it may be ob- 

 served, no relation whatever to the " claw " or nail of the pollex, which 

 is also present, though small, in all the three genera I have examined. 

 The " spur," in Parrajacana at least, consists of an external, translucent, 



