BIRDS OF PREY. FALCONID^. 319 
will be remembered that tbe distinguishing character of 
this type, in the Falconidce, is an extreme shortness of 
foot ; and the discovery of Aviceda, in all other respects 
a perfect falcon, and its most remarkable similarity in 
other respects to Cymindh-, has led us to believe that 
the other tenuirostral types in the genera Accipiter, 
Aquila, Cymindis, and Buteo, would also exhibit the 
same peculiarity. Hitherto, however, we have failed 
in meeting with any forms sufficiently approaching this 
structure, to authorise their insertion in these particular 
stations. Among those genera already proposed which 
we have not personally examined, our suspicions point 
to Asturina and Circeetus of M. Vieillot, and to the 
Buteo pteroeks, as likely to fill up some of these 
stations. 
(255.) The primary object, however, which we have 
had in view, and which has alone tempted us, in this 
stage of our researches, to lay the foregoing exposition 
before the ornithologist, has been that of determining 
the types of the five great divisions of the FaUionida;, 
and of establishing their analogies with all other cir- 
cular groups (through the medium of the Imessores) in 
such a way that nothing yet known should invalidate 
the correctness of the series. ATe therefore wish it to 
be understood that almost every thing beyond this re- 
quires additional verification. Nothing is more difficult 
in natural groups like this than to determine the precise 
location of any particular type ; although %ve may have 
little or no doubt as to the nature of that type. To 
illustrate this remark more fully, — for it deserves the 
greatest attention from ornithologists, — we may instance 
the common kite. Now it is quite clear that this bird is of 
the fissirostral structure*; but whether it belongs to the 
circle of Buteo or to that of Cymindis, would have been 
a matter of very great doubt but for Nauclerus, a sub- 
genus which is evidently more closely related to Cy- 
mindis and FJanus than is Milms. Nauclerus, con- 
sequently, must be considered the fissirostral type of 
* See Classification of Animals. 
