362 University of California Publications in Zoology [Vol. 13 



wider light interspaces, as for instance, in the breast of Goura (pi. 

 29, fig. 66&-c). It is very unusual, in parti-colored barbules, for 

 any pigment to be present ventral to the row of nuclei. A beau- 

 tiful, delicate olive color is produced in the coverts of Osmotreron 

 by distal barbules in which the base is bluish gray, due to cross- 

 bars of black pigment, while the entire pennulum contains a deep 

 lemon-yellow pigment (pi. 29, fig. 69a). The iridescent neck feathers 

 of Columba, Zenaidura, and other genera are produced by 

 barbules from which the pennula are broken off, the reflecting sur- 

 face being the large recurved flange. The barbule drawn on plate 

 29, figure 57&, from a neck feather of Columba fasciata is seen in 

 side view, and nothing of this portion except the tips of the ventral 

 teeth shows as the barbules lie in the vanule, the result being that 

 these feathers are not iridescent on the ventral side (see also Strong 

 1903&). 



e) Relationships 



The Pteroclo-columbae, according to their feather structure, 

 show more similarities to the gallinaceous birds than to any other 

 group. The shape of both distal and proximal barbules, and the 

 specialized nature of the down, are ail points of striking likeness. 

 The occurrence in the tinamous, which are undoubtedly a special- 

 ized group of gallinaceous birds, of both the columbid and galline 

 type of down, might be considered a further bond of union between 

 the two latter groups. They show the same affiliation to some of 

 the gruiform birds as do the gallinaceous birds, and like the latter 

 show some affinity to the Cuculiformes, especially in the presence 

 of prongs on the booklets of the distal barbules of back and breast 

 feathers. The relation of the Pteroclo-columbae to the Laro-limi- 

 eolae, if there is any close relationship, is not shown at all in the 

 structure of the feathers. The Pterocles show a number of differ- 

 ences from the Columbae in feather structure, which are probably 

 specializations of their own, and do not show closer approximation 

 to any other group. 



f) Summary 



(1) Plumules sparse or absent. 



(2) Aftershaft rudimentary or absent. 



(3) Distal barbules of remiges with short, broad base, nuclei in 

 strikingly diagonal line, ventral teeth broad and triangular; pen- 



