﻿BIRDS OF PREY. FALCONIDiE. 319 



will be remembered that the 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 Cymindis, 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 Circcetus of M. Vieillot, and to the 

 Buteo pterocles, 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 Falconidce, 

 and of establishing their analogies with all other cir- 

 cular groups (through the medium of the Insessores^) in 

 such a way that nothing yet known should invalidate 

 the correctness of the series. We 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 we 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 Elanus than is Milvus. Nauclerus, con- 

 sequently, must be considered the fissirostral type of 



* See Classification of Animals. 



