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ON THE CLASSIFICATION OF BIRDS. 



the genus Psaris, for instance, there is a very slender, 

 lanceolate feather inserted between the first and second 

 quills, which seems totally useless for any purpose of 

 flight, but which must have some especial reference to 

 the habits of these birds. The second quill of the 

 white-headed tody of the old authors* is precisely of the 

 same structure as that seen in Psaris, yet here it is not 

 shorter, but longer than the preceding, and therefore 

 must be used as much for flight as an ordinary quill. 

 The four first quills of the Pipra pareola are nearly of 

 the same shape as the preceding, that is, remarkably nar- 

 row and pointed, while the fifth and those which follow 

 are of the ordinary breath ; these narrow quills, moreover, 

 have their outer web indented like the blunt teeth of a 

 little saw, a circumstance that has never been noticed, 

 and which is highly curious. In the genus Oocyrhynchus, 

 the outer web of the first quill is constructed precisely like 

 that of the owl, the lip of each lamina being curved back, 

 in the shape of a hook. Sometimes, on the contrary, one 

 half or more of some of the quills are of the usual breadth, 

 while their terminating end is suddenly contracted 

 and obtusely pointed (fig. 48.) : this formation is seen in 

 some few species of the exotic pigeons belonging to the 

 genera Peristera (a) and Ptilonapus (6). It cannot, how- 



ever as some have imagined, be taken as a subgeneric cha- 

 racter, because perhaps the next species in the series has it 

 not ; and it is probably only a sexual distinction. The 

 Cassicus coronatus of Mexico shows us another example 

 of unequally formed primaries. These are instances of 

 unusual narrowness. Among those of an opposite descrip- 



* The situation of this curious bird is uncertain. It may probably 

 enter into the circle of the Fluvicolince, or water chats. 



