1876.] OF ^GITHOGNATHOUS BIRDS. 257 



liarities of the skull that belong to certain groups of families, which 

 will, when once understood, be very helpful to Taxonomists. These 

 more minute researches go to modify some of Professor Huxley's 

 views, as expressed in his paper ' On the Classification of Birds ' 

 (P. Z. S. 1867, p. 415). Certain it is that the skull of a bird often 

 seems to harmonize very ill with the rest of its structure, even with 

 the rest of the skeleton. Still the morphology of this chief part of 

 the framework, modified as it is in relation to the nervous, digestive, 

 and respiratory systems, must be of the utmost importance to any 

 one seeking to have broad views on these subjects. 



"The groups formed by cranio-facial characters have a variable 

 value ; the desmognathous face passes over the Struthious border and 

 is possessed by the gallo-struthious Tinamous. The saurognathous 

 face (see Trans. Linn. Soc. 1875, plates i.-v.) is possessed by the 

 " Celeomorphse " only — namely, by the Woodpeckers and Wry- 

 necks. 



" The segithognathous face is possessed by all the ' Coraco- 

 morphae,' and by them only, in a perfect form, with the single 

 exception of the Swifts (Cypselidse) — a mere big * genus ' capable 

 of being cut up into a few subgenera. 



" The desmognathous face turns up in many places ; its funda- 

 mental or embryonic form is the schizognathous, the simple rep- 

 tilian cleft palate ; this becomes desmognathous by ankylosis of the 

 right and left elements of the palate. Desmognathism is seen in 

 the iEgithognathse when ossification is very intense, as in Artamus, 

 Paradisea, and Gymnorhwa. 



" The simple, open, or cleft palate generally occurs in the groups 

 that lie on a level two or three degrees above the Ratitse, as Rails, 

 Plovers, Cranes, and the Fowl tribe ; but it is also retained in types 

 that in other respects are amongst the highest and most specialized, 

 as the Trochilidae and the Caprimulgidse. 



" In the present paper research has been made into the morpho- 

 logy of the skull in the following groups — namely Tanagridse, 

 Brachypodidge, Phytotomidse, Mehphagidse, Mniotiltidse, Coerebidse, 

 Vireonidse, Cardinalis, Icteridae, Emberizidae, Fringillidse, Alaudidae, 

 Paridae, Panuridae, Cypselidae, Hirundinidae, Oriolidae, Motacillidae, 

 Muscicapidae, Liotrichidae, Saxicola, and Nectariniidae. 



" And, lastly, the remarkable skull of Thinocorus is described, a 

 small Chilian type, whose body is thoroughly Charadrian, but whose 

 head is a mysterious mixture. Being imperfectly aegithognathous, 

 it is here compared with the completely segithognathous Passerine 

 types on the one hand, and on the other with birds much nearer akin, 

 namely the Crane and the Sun-bittern. These latter, in an appen- 

 dix, serve to compare with Thinocorus, and also show the schizo- 

 gnathous palate for comparison with the more complex palate of a 

 Passerine bird. 



" Thinocorus, whilst essentially a Plover, if the characters of the 

 skeleton generally be considered, yet shows more likeness in its 

 skull to that variety of the Plover type which we see in the larger 

 Cranes. 



Proc. Zool. Soc.~1876, No. XVII. 17 



