Pterylufjraphy of the Tinamiformes. 11 



both of the nietacarpo-digital aud cubital remiges, are of 

 considerable length. 



Tectrices. — Obviously nothing very definite can be said 

 about these feathers at this stage. On the dorsal surface 

 the "downy " major coverts of the cubitus are longer than 

 the remiges, if we may so speak of them. This is inter- 

 estingj as these portions obtain in the development of these 

 feathers in other birds not at all allied. The length of the 

 " down'''-feathers agrees approximately with that of the 

 definite feather which supplants it. 



The Structure of the Nestliny-down. — The structure 

 of the nestling-down is of peculiar interest on account of its 

 unusual complexity. In both Calodromas elegans and 

 Nothura maculosa the nestling-down is found to be not 

 of the usual " downy " character^ but composed of semi- 

 plumes. 



Briefly, a semiplume differs from a down-feather in that 

 in the former the rhachis is long and stiff, supporting several 

 pairs of similarly stiff radius-bearing rami, whilst in the 

 latter the rhachis, if present, is never stiff, and the rami and 

 radii are long and very delicate, hence the loose flowing struc- 

 ture. A Marabou -plume and a piece of Swanks-down well 

 illustrate the two types. 



Probably the first point which would be noticed in an ex- 

 amination of an individual feather would be the enormous 

 aftershaft (PI. III. fig. 1, H.), which almost equals the 

 main feather in size, the difference in length being very 

 slight. The main feather is composed of a strong shaft, 

 bearing four to six pairs of rami, which decrease in length 

 from below upwards, the free ends giving a gently rounded 

 outline. The rami all bear radii, which are longest on the 

 proximal rami. The rami are produced beyond the most 

 distal radii into long filaments^. By the unaided eye the 

 feathers of the dorsal surface can be sharply difterentiated 

 into a distal pennaceous and a proximal downy half; this, of 



* In the nestling Ostrich apparently these filaments become much 

 thickened and flattened out, giving the bird the appearance of having 

 been decorated with thin curly horn-shavings. 



