166 TOD US. 



diminutive, not more than three inches and a quar- 

 ter long, of which the head and bill actually occu- 

 pies one inch and a tenth, or nearly one-third the 

 length of the entire bird. It differs also from 

 all the other species in having the bill more gra- 

 dually attenuated in its breadth as it approaches 

 the end ; just, in short, as that of Conopophaga, of 

 which it becomes, by its very short tail, large head, 

 and bristled front, the complete prototype. Never- 

 theless, the sides of the mouth are strongly bristled, 

 and the tarsi are considerably shorter than those of 

 its congeners. Now, all these variations from the 

 typical species are absolutely necessary to the har- 

 mony of nature. They indicate, as plainly as pos- 

 sible, that this bird is an aberrant species, and thaf 

 it is of the fissirostral or aquatic type. Nor can it 

 possibly be removed from this position among the 

 todies, since there are now before me three other 

 species which establishes the gradation between 

 melanocephalus and megacephalus in the most deci- 

 sive manner. And yet, if the bills of these two 

 kindred species are viewed separately, one might 

 be tempted to place them in different genera. The 

 situation, also, of Todus megacephalus in the se- 

 ries of species, is further confirmed by the structure 

 of T. platycircus, which, from being clearly a re- 

 presentation of the Rasores, will stand at the opposite 

 side of the circle to that of Megacephalus; the gral- 

 latorial, or intervening type, as before observed, 

 being wanting. We thus find, that even in a sub- 

 genus the variations are sufficiently marked to give 



