Anatomy of Acanthidositta cliloris. 619 



the Synallaxine forms it is of great width, owing to the fact 

 that the ischium sends down on to the pubes a long slender 

 rod of bone. In Pipra, as in Acanthidositta, the transverse 

 processes of the synsacrum decrease in length from the 

 sacral region backwards ; but the innominate of Acanthi- 

 dositta is peculiar, in that its dorsal plane is very narrow. 

 The pre-ilia are widely separated and relatively short. The 

 ischia are produced backwards fur a considerable distance, 

 lying parallel with the pubes, and thus practically closing 

 the ischio-pubic fissure. The pubes are moderately long, 

 slender, and bowed slightly downwards. 



Summary. 



It is now just seven-and-twenty years ago since Forbes (2) 

 laid the foundation-stone of our knowledge of the anatomy 

 and systematic position of Acanthidositta and Xenicus. 

 These curious forms had hitherto been referred to a position 

 within the " Certhiidce " — an " Oscinine " group, with which, 

 as Forbes shewed, they have nothing whatever to do. " As 

 regards the affinities of the Xenicidce" wrote this author, 

 " the ' haploophone ' form of their syrinx, combined with the 

 complete loss of a vinculum, shews that it is only with the 

 Piprida (including the Cotinyidce), Tyrannida, Pittida, and 

 Philepittida that they can be compared. From all of these 

 they differ markedly, however, in the number of rectrices, 

 the ocreate tarsus, and the nature of the syrinx, the latter 

 never having the form of a complete bony box, and never 

 lacking a bronchial { intrinsic' muscle in any of the 

 families just enumerated. The Pittida they approach some- 

 what in their general fades, short tail, and long tarsus, 

 though the tarsal scutellation is different in the two forms." 



My own conclusions on this matter do not altogether 

 harmonise with those just quoted. The evidence, I venture 

 to think, rather favours the view that the nearest allies of 

 these birds are the Furnariida; of Garrod. The same form 

 of the maxillo-palatiue processes and the schizorhinal nares 

 seem to be met with in all the Furnariida; and in Acanthi- 

 dositta. The peculiar form of the nares was, by the way, a 



