PROF. W. K. PAEKEE ON ^GITHOGNATHOUS BIRDS. 293 



a. Direct, as in the Falcons and Geese, when the maxillaries meet below at the 

 mid line, as in the mammal : two subvarieties of this form occur, as in the Falcon, 

 where the nasal septum is ankylosed to this hard palate ; and in the Goose, where it 

 remains free. 



h. Indirect. — This is very common and is best seen in Eagles, Vultures, and Owls ; 

 the maxillo-palatines are ankylosed to the nasal septum by their inner margin, but 

 are separated from each other by a chink ; this is well seen also in the fledgeling of 

 the Falcon, which is indirectly desmognathous at that early stage. 



c. Imperfectly direct. — This is when the maxillo-palatine plates are united by 

 harmony-suture, and not by coalescence. Example Dicliolophus cristatus. 



d. Imperfectly indirect. — Here the maxillo-palatine plates are closely articulated 

 with and separated by the " median septo-maxillary " bone, but these are not ankylosed. 

 Example Megalcema asiatica. 



A fifth variety might have been added, in such a case as Podargus, where the 

 palatines as well as the maxillaries largely coalesce below ; to a less extent this is seen 

 in the gigantic species of Hornbills, e. g. Buceros birostris (see Huxley, t07n. cit. p. 446. 

 fig. 28). 



Podargus carries this desmognathism to the greatest extent of any bird ; in the 

 Crocodile, and in the Anteater, a still more extended hard palate occurs, where the 

 internal pterygoid plates form a lower bridge. 



The unpublished materials from which I have made these extracts illustrate several 

 forms of desmognathism, besides the early conditions of the segithognathous palate 

 and such schizognathous fonns as Trochilus and Caprimulgus. 



I have already given several figures of the schizognathous palate in my former 

 paper, " On the Gallinaceous Birds and Tinamous " (Trans. Zool. Soc. vol. v. pi. 40). 

 Here pi. 37 illustrates Syrrhaptes and Lagopus, and pi. 38 Vanellus and Columha ; 

 pi. 40 gives the struthious or dromseognathous face of Tinamus. But the most familiar 

 and simple illustration of the schizognathous face is seen in the Fowl (Phil. Trans. 

 1869, pis. 81-87). 



These details of morphology have to be mastered before the taxonomic value of 

 these facial characters can be known, or in any way appreciated ; and they are matters 

 that lie somewhat deeper than the length or thickness of a primary quill, or the 

 direction of the outer toe. 



The materials out of which the segithognathous face has been formed, exist, in a raw 

 state, in the reptiles (Lacertilia, Ophidia) and, still nearer home, in the Rhea. 



The counterparts of the cartilages in which the first osseous centre for each " vomer " 

 is found in the " ^githognaths," were long since figured by me in the Ehea (Phil. 

 Trans. 1866, pi. 10. fig. 14, alate sections on each side of r.b.s and v), and also were 

 found in the common Snake (Natrix torquata) and in the embryo of Eunectus murinus ; 

 these studies of the Ophidian face have not, however, been published. 



