A PECULIARITY IN THE GROWTH OF THE TAIL FEATHERS 

 OF THE GIANT HORNBILL (RHINOPLAX VIGIL). 



By Alex Wetmore, 



Of the Biological Survey, United States Department of Agriculture. 



Sometime ago Dr. C. W. Richmond, of the United States National 

 Museum, called my attention to certain pecuharities in the rectrices of 

 the Giant HornbiU (Rhinojjlax vigil) and the following notes are the 

 outcome of his kindness in allowing me to examine the material under 

 his care ^ Nine specimens, six males and three females, of this fine 

 bird are at hand, aU collected by Dr. W. L. Abbott. In none of these 

 are the rectrices perfect as will be noted in the detailed description 

 below, and it was this fact that first drew attention to them in Doctor 

 Richmond's search for a specimen to be mounted and placed on gen- 

 eral view. The elongated median tail feathers at once catch the 

 attention on examining this Hornbill, and their length is no less 

 extraordinary than the apparent manner of their growth to which I 

 believe attention has not been called previously. 



Ten rectrices are found in the completely developed tail of this bird, 

 eight outer feathers of moderate size and two central feathers, which 

 when completely developed, are from 2 to 3 feet in length. The only 

 apparent difference between male and female in the growth of the tail 

 is that of relative size, the male being the larger bird. 



Folloudng is a brief description of the condition of development of 

 the caudal feathers in the specimens at hand, arranged in chrono- 

 logical sequence: 



Cat. No. 159447, U.S.N.M.; female; Lay Song Hong, Trong, 

 Lower Siam, September 16, 1896. The eight lateral tail feathers are 

 all present but of the central pair, one long feather, faded in color and 

 somewhat worn, is developed. On the right side a second long 

 feather, bright and new in color, is growing with its tip about one and 

 one-half inches beyond the shorter lateral feathers. 



Cat. No. 159448, U.S.N.M.; male; Lay Song Hong, Trong, Lower 

 Siam, September 24, 1896. The eight outer rectrices are fully grown 

 and one long central feather somewhat worn appears on the left side. 



To Mr. H. C. Oberholser thanks are due for suggestions during the preparation of this paper. 



Proceedings U. S. National Museum, Vol. 47— No. 2059. 

 34843°— Proc.N.M.vol.47— 14 32 497 



