PSITTACUS ERITHACUS. 171 



right foot, the female the left. There is no rule. Of course, if a bird is 

 fastened by the foot it usually employs, it is greatly inconvenienced. 



In Psittacus eritJiacus we find a difference in the colour of the iris, 

 arising from age. Mr. Bartlett is much of opinion that in some of the 

 Cockatoos (Cacatuinse) a sexual variation exists ; and in this he is confirmed 

 by John Goss, the keeper at the Zoological Gardens, who after forty years' 

 observation must have had good opportunity of knowing. They express 

 their belief that this is the case in a pair of Citron-crested Cockatoos, Timor 

 (^Cacatua cilrino-cristatd), thinking them to be male and female because they 

 agree well together. In the Lesser Sulphur-crested Cockatoo QCacatua 

 sulphur ea} an instance was pointed out to me where the male had a blue- 

 black eye, while in the female the iris was red. 



In the three British Harriers (^Circus), Mr. J. H. Gurney states (" Notes 

 on Mr. R. B. Sharpe's 'Catalogue of Accipitres,' " 'Ibis,' April 1875, 3rd 

 ser. vol. V. p. 222), " the colour of the iris in the adult is always a clear 

 yellow in the males, and usually a yellowish broAvn in the females ; but it 

 would seem that in the latter, as they become aged, the colour of the iris 

 approaches nearer to that of the male bird ; and this is especially the case in 

 Montagu's HaiTier." 



Dr. Otto Finsch has given a fine Plate of the skeleton of this Parrot 

 (' Die Papageien,' vol. i. p. 240), with skulls of PlictolopJms sul/ureus and 

 Euphema pulchella. 



Mr. A. H. Garrod, in the ' Proceedings of the Zoological Society ' (1873, 

 p. 557), on the carotid arteries of birds, says : — " The Parrots are peculiar 

 for the variation which occurs in their carotids, which show four different 

 arrangements : first, there may be two in the normal position ; secondly, the 

 right may (as it usually does) traverse the hypapophysial canal, whilst the 

 left, in a manner quite exceptional, runs superficially along the side of the 

 neck in company with the left pneumogastric nerve and the left jugular vein ; 

 thirdly, the right may be very small and blend with the much larger 

 normally situated left (in Cacatua sulphurea, according to Meckel) ; and, 



