174 STRUCTURE AND CLASSIFICATION OF BIRDS 



femoral feathering ; but apart from this the same type of 

 pterylosis occurs in many types, such as Motacilla, Certhia, 

 Oriolus, &c. The principal variation is offered by those 

 passerines in which the spinal widened area is not solid, but 

 encloses a space. 



We find this in Coracina cephaloptera and Seleucides. 

 In others (e.g. Eurylamus) there is the same ephippial space 

 within the dorsal tract, but the posterior sides of the diamond- 

 shaped space are formed by a single row of feathers, which 

 contrast with the mass of feathers which form the antero- 

 lateral boundaries of the space. This arrangement culmi- 

 nates in, for example, Hirundo and Diphyllodes, where the 

 dorsal tract forks, and there is no connection between the 

 ends of the fork and the single posterior part of the spinal 

 tract.' 



The skull of Passeres has been mainly investigated by 

 Paekbr and by Shufbldt.^ Corvus may be taken as a 

 type, and the divergences therefrom noted later. As are all 

 passerines, it is eegithognathous ; the maxillo-palatines extend 

 obliquely outwards and backwards ; they approach each 

 other in the middle line, and expand over the vomer. The 

 vomer is broad and bifurcate both anteriorly and posteriorly ; 

 from the anterior horns a small separate piece of bone goes 



' For passerine pterylosis, see, in addition to Niizsch, Gieeel, ' On Ptery- 

 losis of Paradisea,^ Zeitschr. f. d. ges. Naturw. xlix. p. 143, and for Philepitta 

 ibid. p. 490 ; Shufelet has described Chamcea, Joum. Morph. iii. 18R9, p. 

 475'; Hellmann, ' Beitrag zur Ptilographie u. Anatomie der Hirundo rustica,' 

 J. f. 0. iv. 1856, p. 360 ; Gadow, ' Remarks on the Structure of Certain Hawaian 

 Birds,' in Wilson and Evans's Aves Hawaienses, ii. Sept. 1891. 



" For osteology of Passeres see Parker, ' On the Structure and Development 

 of the Crow's Skull,' Month. Micr. Jqurn. 1872, p. 217 ; ' On the Development 

 of the Skull in the Tit and Sparrow Hawk,' ibid. 1873, pp. 6, 46 ; ' On the 

 Development of the Skull in the Genus Turdus,' ibid\ 1873, p. 102 ; ' On 

 iEgithognathous Birds,' Trans. Zool. Soc. ix. p. 289, x. p. 251 ; Mukie, ' On 

 the Skeleton and Lineage of Fregihipus,' P. Z. S. 1874, p. 474. Lucas, 

 ' Notes on the Osteology of the Thrushes,' &b., P. U. S. Nat. Mies. xi. 1888, p. 

 173. 



Shcfeldt, "' Osteology of Eremophila,' Bull. U. S. Geol. Surv. vi. p. 119 

 ' Osteology of Lanius,' ibid. p. 351 ; ' On the Skeleton in the Genus Sticr 

 nella,' &c., /. Anat. Phys. xxii. p. 309 ; ' Osteology of Sabia Atik,' v. p. 438 

 ' Osteological Notes on Puffins and Ravens,' ibid. p. 328 ; Giebel, ' Zur Osteo- 

 logie d. Gattung Oaypterus,' -Zeitschr. f. d. ges. Naturw. xxi. p. 140. 



