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VIII, On the Structure and Development of the Skull in the Ostrich Tribe. By William 

 Kitchen Paeker, F.Z.S. Communicated hy Professor T. H. Huxley, F.R.S. 



Eeceived February 23, — Read March 9, 1865. 



Introduction. 



The present paper is intended to be the first of a series on the Anatomy of the Verte- 

 brate Skull ; and I have chosen the cranium and face of the Ostriches as a starting- 

 point, principally because of the mid position of these birds in the vertebrate sub- 

 kingdom, and, in some degree also, because of their generalized character. Indeed, to 

 any one familiar, on the one hand, with the structure of the skull in the higher mam- 

 malian types, and on the other mth that of the osseous fishes, the skull of an Ostrich 

 is interesting and important in a very high degree ; serving, at it does, as a key to open 

 up the meaning of parts so extremely unlike as the true homologues in the Fish and in 

 the Mammal often are. And further, whilst aiding the anatomist in revealing the true 

 morphological counterparts in the highest, as compared with the lowest types, the skull 

 of an ostrich does also form a link of the utmost value for connecting together that of 

 a cold-blooded and that of a warm-blooded creature. 



I hope to follow up this first paper by one on the development of the skull and face 

 in the Common Fowl, and this for two reasons ; first, because this bird is the most 

 available, in all its stages, to the morphologist, and also because it takes us further 

 up amongst the branches of the great ornithic tree ; leading us by gentle gradations 

 towards those higher types in which the feathered tribes culminate. 



Afterwards the " Sauropsida," as a whole, being one of the three great primary 

 divisions of the Vertebrata, may be investigated still more completely ; then the Mam- 

 malia, and ultimately the " Ichthyopsida." I may mention that the material for these 

 papers is not altogether wanting ; but much more research is needed to make it avail- 

 able for the purposes of science. 



Having laboured much at the Fishes, I naturally look at the skull of the Bird with 

 the eye of an ichthyotomist : this will explain why certain terms, either new to anato- 

 mical science, or only existing in my own published papers in the Transactions of the 

 Zoological Society, have been used. For although the true counterpart of some bone, 

 distinct and well known as to its mere form in the lower classes, may exist in the 

 Mammalia, yet if it be not autogenous in them, but existing as a mere outgrowth of some 

 other, then the distinct bony piece of the lower type of vertebrate must have its own 

 proper name, and cannot be described as ^. process or outgrowth. 



In the present paper I shall have to speak of a bone which, although distinct in 



MDCCCLXVI, S 



