188 



PLATYSTERA. 



IN proportion to the number of species which 

 enter into a group, so do we invariably find a pro- 

 portionate degree of variation. Applying this uni- 

 versal law to the assemblage of birds forming the 

 genus Todus, we observe that as the typical sub- 

 genus contains the most in number, so does it ex- 

 hibit the greatest variation of structure. Platystera^ 

 in like manner, ranks the next in extent, and we 

 have thus been able to detect three distinct modifi- 

 cations of its typical characters. We have no doubt 

 that several other species exist of this group ; one 

 is obviously the Molenar of Le Vaillant, and we 

 suspect the Capuchon blanc (PL 159.) may be an- 

 other, although the presence of a crest is much 

 against the supposition. All these we have de- 

 scribed from the birds before us, but no public or 

 private collection, however large, can be supposed 

 to contain every thing. "We must, therefore, now 

 have recourse to our notes, among which we find 

 the following, made some years ago, in the early 

 stages of this analysis. " Platystera is united either 

 to Conopophaga or to Platyrhynchus by a bird in 

 the British Museum which belongs to Platystera, 

 but which has a very short tail ; short, unequal, 

 and syndactyle toe, formed for perching, and quite 

 as much united as those of T. viridis." Here, then, 

 is the fissirostral type of Platystera^ approximating 



