98 



cenchrdides (Falco cenchrdides of Messrs. Vigors and Horsfield,) ex- 

 hibits a beautiful analogy with the Common Kestril of our island, 

 but although nearly allied possesses several important and permanent 

 difFerences. 



" The great variety of changes to -vvhich the members of the genus 

 Astur are subjected, has led to vast confusion, and it is only by a 

 minute examination of the numerous examples in my coUection in 

 various stages of plumage, that I have been able to determine the 

 species with satisfaction to myself ; and if I have found it necessary 

 to consider as identical two or three species of this genus charac- 

 terised by Messrs. Vigors and Horsfield, I feel confident that it was 

 ovving to the absence of sufficient materials at the time the Linnean 

 collection was so ably named by those gentlemen, that they were 

 described as distinct. 



" My attention has of coursebeen directed to the great difference 

 in size \vhich exists between the malęs and females, and the various 

 changes from youth to maturity which occur in the members of the 

 genera Astur and Accipiter, and I mušt now call the attention of 

 the members present to the beautiful analogy which exists bet\veen 

 the Acdpiter torquatvs and the Astur approximans of Messrs. Vigors 

 and Horsfield, of which several exaraple3 are on the table ; I say 

 analogy, because it is in colour alone that so great a simUarity exists 

 between them. These gentlemen having applied the names of ap- 

 proximans and f asciafus to two birds which I believe to be synony- 

 mous \vith the Falco radiatus of Dr. Latham, •vvhose description was 

 taken from a young bird, I retain the name of Astur approximans in 

 preference to radiatus, from the near approach of these two birds to 

 Accipiter torąuatus. It will, perhaps, not be out of place to say a 

 few words on the difference in structure of these birds, which in 

 outvvard appearance offer so close a resemblance to each other. The 

 females in both these minor groups far exceed the malęs in size, and 

 both groups appear with a trifling deviation to be subject to the šame 

 changes of plumage ; while in their structure they exhibit con- 

 siderable differences, the chief of which are the more delicate, 

 slender, and lengthened form of the legs of Accipiter, the great pro- 

 longation of the middle toe, and the square or forked form of the 

 tail. On comparison it will be found that the centre toe of the little 

 malė Accipiter on the table is fully as long as that of the malė Astur 

 approi'imans, a bird nearlj' double its size ; that the tarsi in the latter 

 bird are comparatively shorter and more robust ; and that the middle 

 tail-feathers are the longest, gi\"ing a rounded form to that organ. 



" It may be truly said that Australia abounds in anomalies, -vvitness 

 its Black S\van and White Hawk, which latter bird has not a little 

 puzzled me, and I am not yet satisfied as to -vvhether it be not a per- 

 manent albino variety of auother species, examples of ■vvhich are now 

 on the table •with a con-esponding number of birds in the white plu- 

 mage. Much difference will be found in their size, but this may be 

 readily accounted for by the difference of size in the two sexes. 



" The malęs and females of the white birds agree so accurately in 

 their measurements with those in the grey plumage, as to induce me 



