ON THE STOMACH IN TANAGERS. 133 



diminutive size must always make this a very well-marked genus. But 

 I fail to see in its spiny tail sufficient importance to elevate Nasiterna 

 into a special subfamily, as suggested by Mr. Sclater. Chcetura is not 

 separated on similar grounds from the other Chaeturinsa ; nor has the 

 spatulate tail of Prioniturus been advanced as entitling that genus to 

 form a special subfamily. 



The anatomy of the small short-tailed genera Cydopsitta, Psittacella, 

 &c. is as yet unknown ; but I believe that it is amongst these forms 

 related, as far as can be judged from external appearance, through this 

 last to Pezoporus, Geopsittacus, &c. that Nasiterna has its nearest allies. 

 Ayapornis and Psittinus are also not very distantly related, though I 

 believe that the loss of its furcula by Ayapornis, in which it resembles 

 Nasiterna, is probably due to independent causes *. That the loss of 

 the furcula is not exclusively correlated with terrestrial habits is shown 

 by its absence in three such essentially arboreal genera as Ayapornis, 

 Nasiterna, and the Neotropical Psittacula. 



24. CONTRIBUTIONS TO THE ANATOMY OF PASSE- 

 BINE BIRDS. PART I. ON THE STRUCTURE OF 

 THE STOMACH IN CERTAIN GENERA OF TANA- 

 GERS.f 



UNDER this heading I propose to continue from time to time, as material 

 may occur, the "Notes on the Anatomy of Passerine Birds," of which 

 the late Prof. Garrod published four parts in the Society's ' Proceed- 

 ings ' +. 



In the vast majority of Passerine birds the structure of the anterior 

 part of the alimentary canal conforms to the type present in the Fowl 

 that is to say, to an oesophagus, which may or may not be dilated into a 

 crop, succeeds a stomach consisting of two parts : an anterior glandular 

 part, the proventriculus ; and a posterior part, separated off from both 

 proventriculus and duodenum by more or less distinct constrictions the 

 gizzard or ventriculus, of which the muscular walls are always more or 



* Judging by its behaviour in captivity, Agapornis is extremely sluggish in its 

 movements. 



t Proc. Zool. Soc. 1880, pp. 143-147. Read Mar. 2, 1880. 



| Part I. P.Z. S. 1876, p. 506; Part II. 1877, p. 447; Part III. 1877, p. 523; 

 Part IV. 1878, p. 143. 



