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YII. On the Structure and Development of the Bird's Skull. By W. K. Parker, 

 F.B.S., F.L.S., §rc. (Part II.) 



(Plates XX.-XXVII.) 



Bead December 16th, 1875. 



Introductory Remarks. 



IN a paper of mine on the Development of the Bird's Skull (Phil. Trans. 1869, pp. 755- 

 807), a single species, the Common Fowl, was used as the subject ; this was worked out 

 to as great an extent as was possible to me at the time. 



Year by year since then steady work at other types of the Yertebrata has, by letting 

 in fresh light, shown me some serious deficiencies in that paper, and my mind has not 

 been able to rest without an attempt to superadd something of value to the older piece 

 of research. 



I may at once remark that, criticising this my own work, I find that the eye and the 

 hand had done their work better than the mind ; the plates are clearer and truer to 

 nature than the descriptions. 



The Memoir which followed that on the Skull of the Fowl treated of this part in the 

 Common Prog, a type so diverse from that of the Vertebrata generally as to mislead me 

 somewhat in my comparisons, and to make me doubt the correctness of my earlier 

 descriptions. Purther researches, however, have set my mind at ease on several points, 

 notably those on the Salmon's Skull (Phil. Trans. 1873, pp. 95-145, plates i.-viii.). 



There was another reason, however, why it was desirable to supplement the paper on 

 the Skull of the common Gallinaceous bird, namely, that it is itself a very simple senii- 

 struthious type, and conveys but an imperfect idea of the remarkable metamorphoses the 

 lleptilian type of skull can undergo when subjected to the intense life-energy of a high- 

 class perching or climbing bird. 



A third reason has acted as a propelling force in this matter : this was a strong desire 

 to clothe with flesh and form the masterly skeleton paper on the " Classification of 

 Birds" given by Professor Huxley to the Zoological Society a few years ago (Proc. Zool. 

 Soc. 1867, pp. 415-472). 



In that paper the palatal structures are chosen as the ground of classification ; and 

 although, to a hasty observer, these might seem to be a mere fragment of the whole bird, 

 yet they are, indeed, the parts to which all others follow suit — the upper jaw and palate, 

 the first and part of the second facial arch. To these parts every thing else in the Bird is 

 correlated ; they rule, as it were, the whole economy of the Bird. 



Renewed researches, which have been zealously followed up by me for some years, on 

 the structure and development of the " trabecule cranii," " pterygo-palatine arcades," 

 and nasal labyrinth, have yielded results that seem to me to be of great value. 



SECOND SERIES. — ZOOLOGY, VOL. I. P 



