TO BIRD-ANATOMY AND CLASSIFICATION. 205 



combinations of characters so obtained a scheme of classification is 

 sketched out, each group having assigned to it a formula stating its 

 most essential characters. The presence or absence of the ambiens 

 muscle, of a furcula, and of an oil-gland are the points here laid stress 

 on, together with the condition of the carotid arteries. Of these there 

 may be either two normally situated, or only one, the left (Cacatua and 

 Licmetis tenuirostris), or two, the left of which, instead of running with 

 its fellow in the hypapophysial canal, as already explained, runs 

 superficially up the neck with the left vagus nerve and jugular vein. 

 This last condition, which obtains in no other birds, is considered, as I 

 think rightly, sufficiently important to divide off as a main group of 

 Psittaci all those possessing it a group including all the American 

 Parrots, together with the Platycercidae (including Laihamus), Nestor, 

 Dasyptilus, and the African Parrots, other than Agapornis and Palceornis, 

 of the Old- World forms. The further subdivision of these groups is 

 effected in the way already indicated. In a supplementary note attention 

 is called to the probably invariable presence of a gall-bladder in the 

 Cacatuince, though this organ has not been found in any other Parrots. 

 In a preceding paper* Prof. Garrod has described and figured the tongue Ibis, 1881, 

 of Nestor, which, as he shows, is peculiar, and not like that of the Lories, p * 22> 

 with which it has often been associated. 



6. Otididce^. In Eupodotis australis there is not, as had been 

 supposed, and even stated +, by previous observers, a gular pouch, such 

 as has been seen in Otis tarda. On the contrary, the oesophagus is highly 

 distensile, and so produces the singular appearance of the males of this 

 bird when excited during the breeding- season. In a young male 

 specimen of Otis tarda examined, there is also no gular pouch present ; 

 but the frcenum linguce was double ; and it is suggested that the pouch 

 which has been found in the males of that species is due to a rupture and 

 distention of the mucous membrane between this duplicate feenum, 

 owing to the inflation of the air-passages during the period of display. 



7. Chauna. The pterylosis, visceral anatomy, myology, and cranial 

 and other characters of the Derbyan Screamer are here fully described. 

 The very peculiar nature of the alimentary canal, in the glandular parts 

 of the proventriculus forming, not a zone, but a patch, as well as in its 

 possession of long sacculated caeca, without any spiral valve, which open 

 into a special division of the intestine situated between the colon and 



* " Note on the Tongue of the Psittacine genus Nestor," P. Z. S. 1872, pp. 787-789. 



t "On the 'Showing-off' of the Australian Bustard," P. Z. S. 1874, pp. 471-473; 

 "Further Note on the Mechanism of the 'Show-off' in Bustards," P. Z. S. 1874, 

 pp. 673, 674. 



J Ibis, 1862, p. 114. 



" On the Anatomy of Chauna derbiana, and on the Systematic Position of the 

 Screamers (Palamedeidae)," P.Z.S. 1876, pp. 182-200, pis. xii.-xv. 



