i33 7 .] 



Correspondence. 



267 



a careful study of them for himself. One thing it must point out to all, 

 and that is, for our descriptions of such structures to be broad and full we 

 should have before us, whenever it is possible, abundance of material, — 

 and, too, with respect to measurements, we should aim to establish re- 

 liable standards through the calculation of averages computed from care- 

 fully taken individual data.* 



RIGHT LATERAL VIEW OF THE SKULLS OF \". X ANTIIOCEPHALUS, 

 $ C?.(X2). 



pp, pars plana ; na t nasal ; mxp, maxillo-palatine ; v, vomer ; nix, maxillary ; //, pal- 

 atine ; pt, pterygoid ; ins, manibular sesamoid ; q, quadrate. 



* Since publishing the above in 'Science,' Mons. Alfred Grandidier, Memb. de l'ln- 

 stitute de Paris, writes me from Paris that he fully agrees with me in the marked vari- 

 ation that may take place in the skulls of the same species of birds, and invites my 

 attention to figures \-id of plate 156a of his ' Birds of Madagascar ' ; and to figures 

 2 and 4 of plate 18 of his ' Mammalia of Madagascar.' I regret to say that this well- 

 known work is not before me at the present time. 



