STKIGES 253 



find likenesses than differences. The Aocipitres have rudi- 

 mentary caeca, a biceps slip, the expansor secundariorum, a 

 tufted oil gland, an aftershaft (except Pandion) ; the deep 

 flexor tendons are different, and, in short, the differences are 

 as great as those which separate any two groups of carinate 

 birds.' 



PSITTACI 



Definition. — Tw^elve reotrioes ; •' aftershaft present ; aciuintocubi- 

 tal ; zygodaotyle. Skull desmognatlious, holorhinal, -witli- 

 out basipterygoid processes. Biceps slip and expansor se- 

 cundariorum absent.' Muscle formula, AXTT + or — . Ifo 

 ceeca ; a crop present. 



The parrots are an almost cosmopolitan group, being 

 most abundant, however, in the tropics. Count Salvadoei, 

 in his British Museum catalogue of the group, allows five 

 hundred species, distributed among seventy-hine genera. 

 The parrots are a very sharply defined group, there being 

 no dubious outlying forms. They are -usually brilliantly 

 coloured, and lay white eggs in hollows of trees. With the 

 exception of the owl parrakeet (Stringops) of New Zealand 

 the parrots are arboreal birds, as, indeed, the zygodactyle feet 

 denote. As to external characters, the exaggeratedly hawk- 

 like bill is well known. The almost universal twelve 

 rectrices distinguish the group, but in other external and 

 internal characters the parrots show considerable diversity 

 of structure, as is sometimes the case with large and widely 

 distributed groups ; compare, for instance, the pigeons, which 

 present many other analogies to the parrots. 



The oil gland* is a structure which may be wanting or 

 developed. The table on p. 268 indicates some of the genera 



' See also under ' Caprimulgi,' p. 243.. 

 " " "With the sole exception (of. Gadow) of Oreopsittacus Arfalci. 



^ See below, p. 261. 



* External characters and many other points in the anatomy of parrots are 

 dealt with by Gakkod, ' On some Points in the Anatomy of the Parrots,' &c., 

 P. Z. S. 1874, p. 247, and ' Notes on the Anatomy of certain Parrots,' ibid. 

 1876, p. 691 ; see also Forbes, ' On the Systematic Position of the Genus 

 Lathamus,' ibid. 1879, p. 166, 



