146 Mr. J. H. Gurney's Notes on 



47. PoLYBOROiDEs TYPicus, A. Smith. African Gymnogene. 



Mr. Layard, in common with some other authors, treats 

 the Madagascar race, P. radiatus (Scop.), as identical with the 

 African ; but it seems to me to be, without doubt, specifically 

 distinct, having always, in its adult state, the transverse white 

 bars on the abdomen and adjacent parts conspicuously 

 broader than is the case in the African species, from which it 

 also differs in the paler grey of the upper surface, and espe- 

 cially of the head and neck. This distinction is pointed out by 

 Dr. Hartlaub (Orn. Westafr. p. 3) ; and he adds the follow- 

 ing remarks with reference to this species, to which 1 am de- 

 sirous of calling attention : — 



" In P. typicus there exists, according to a communication 

 from that expert and credible observer, Jules Verreaux, a very 

 remarkable peculiarity, namely that the tarsus at the knee-joint 

 is moveable towards the front as well as behind, a provision 

 which renders no little assistance to the bird in drawing out 

 frogs in its talons from the marsh-holes. . . . Verreaux saw it 

 in such places twist and turn its legs in all directions, and in the 

 most surprising manner, in order to capture its prey.'' 



This singular property has been also observed by Mr. Ayres 

 in Natal (Ibis, 1859, p. 237) ; and a similar observation as to the 

 reversibility of the upper metatarsal joint in the Madagascar 

 species has also been made by Mr. Edward Newton (Ibis, 1863, 

 p. 338). 



Professor Owen, who very obligingly examined, at my request, 

 a skeleton of P. typicus with reference to this peculiarity, in- 

 formed me that : — 



" The peculiar power of reversing the ordinary position of 

 the metatarsus appears to depend, not on any modification 

 appreciable in the configuration of the articular surfaces of 

 the tibia and metarsal bone, but on the smaller size and less 

 cuneiform shape of the fibro-cartilage attached to the inner 

 side of the capsule of the joint, and which is wedged in, in the 

 Kite, Sparrow-Havvk, and, no doubt, in most other Raptures, be- 

 tween the two bones at the back of their joint. No doubt the 

 lateral ligaments would present a correlated modification ; but a 

 dissection of the parts in the recent Polyboroides would be re- 



} 



