206 TROPICAL WILD LIFE IN BRITISH GUIANA 



beyond the hinder edge of the wings. The pelvic wing ' 

 was well marked, and extended from the anterior border 

 of the thigh back almost across the patagium. It consisted 

 of eighteen feathers in an ascending line. The 2nd to the 

 10th had lower coverts, eight in all. 



Five pairs of tail feathers were well developed, and at 

 first glance there seemed to be only four pairs of upper co- 

 verts. Closer observation showed a tiny fifth, pair. The 

 coverts had been puslied up until the two central pairs of tail 

 feathers seemed to be quite covertless. 



I have mentioned the heel pad at the ankle joint. This 

 is a serrated or more properly, toothed pad of horn, capping 

 the joint between the tibio-tarsus and tlie tarso-metatarsus. 

 It fits like the elbow pad of a football player, and during 

 the period when the feet are helpless, it serves as a secondary 

 set of toes, on which the nestling can rest, and awkwardly 

 stump about the nest cavity. 



As tlie egg-tooth of the common chick and indeed of 

 the toucans as well, is a purely enibr3^onic character, so this 

 heel-pad is wholly concerned with the nestling period. It 

 has been briefly described in other birds such as wood- 

 peckers. ' 



The pad is roughly oval and in general appearance re- 

 calls the molar tooth of an elephant. The cusps are variable, 

 there being twelve on the left pad and eleven on the right. 

 The rim of the structure is pale bluisli. The bases of the 

 cusps are yellow, while the face of the large anterior cusps 

 is very hard and pigmented with brownisli black. It is re- 

 markable how close the resemblance is to ])lunt claws or 

 actual teeth. The two anterior ones ha\'e sliarp, projecting 

 cutting edges which catch and hold anything which touches 

 them. 



^ Vide "A Tetraptervx Stage in the Ancostrv i»f Birds," Recbr, 'LiioUxi'ini. 

 II, 1915, pp. 39-52. 



^ Proc. Zool. Soc. London, 11)13, pp. 1095-1096. 



