378 



THE DESCENT OF MAN. 



ored more conspicuously in. the male than in the female; and "the 

 "oblique grooves upon the sides of the lower mandihle are pe- 

 "culiar to the male sex."" 



Fig. 46. Bower-bird. Chlamydera maculata, with bower (from Brehm). 



The head, again, often supports fleshy appendages, filaments, 

 and solid protuberances. These, if not common to both sexes, 

 are always confined to the males. The solid protuberances have 

 been described in detail by Dr. W. Marshall,°° who shows that 

 they are formed either of cancellated bone coated with skin, or 

 of dermal and other tissues. With mammals true horns are 

 always supported on the frontal bones, but with birds various 

 bones have been modified for this purpose; and in species of the 



" 'Land and "Water," 1S68, p. 217. 

 »= Ueber die Sctiadelhoclcer,' &c., 

 log-ie,' B. I. Heft, 2, 1872. 



'Niederlandischen Archlv fur Zoo- 



