VERTEBRATE ZOOLOGY. 479 



Different islands of the Polynesian group have had their 



avifaunas elucidated by O. Finsch, E. L. Layard, and R. B. 



Sharpe. 



The Pubic Bones of Birds. 



It has been generally assumed by anatomists that the pu- 

 bic bones are represented as a whole, in birds, by the elon- 

 gated backward-extending bones parallel with the sacrum, 

 and that they are homologous with the pubic bones of rep- 

 tiles, e. a., but retroverted or bent backwards. It would now 

 seem, however, that this view is not exactly correct. Even 

 in the Dinosaurs of the most generalized structure, the pubic 

 bones, at their bases, are expanded or extend behind the ant- 

 obturator foramina (for the transmission of the obturator in- 

 terims muscles) backwards and downwards beneath the ischi- 

 ac bones, with which they articulate by simple suture, while 

 in the most bird-like types of the same order they extend 

 into elongated processes parallel with the ischiac bones, but 

 only connected by suture below the acetabula. In both 

 types, however, the pubic bones extend dowmvards and for- 

 Avards as is the wont. But while in the generalized forms 

 the posterior or post-acetabular expansions are very short or 

 rudimentary, in the ornithoid forms they have become long- 

 er than the anterior portions. On a renewed comparison, 

 then, with birds, it becomes obvious that the pubic bones of 

 the avian type are not, as a whole, homologous with the 

 principal or anterior portions of the reptilian pubes, but that 

 they must be considered as composed of two parts viz., (1) 

 the anterior or ant-acetabular processes, which are more or 

 less atrophied ; and (2) the posterior or post-acetabular proc- 

 esses, which are excessively hypertrophied. It thus appears 

 that, so far as regards the pubic bones, birds are distinguished 

 by the reversed development of their respective parts. For 

 the basis of this generalization, Ave are indebted to articles 

 on the Dinosaurian Reptiles, by Dr. J. W. Iiulke [Journal of 

 the Geological Society of London, vol. xxxii., pp. 364-366) 

 and Professor O. C. Marsh [American Journal of Science 

 and Arts, vol. xvi., pp. 415, 416, pi. 10). 



The Moulting of Parts of the Corneous Covering* of Bills in Birds. 



Some years ago (in 1874), Mr. Robert Ridgway announced 

 the important discovery that the conspicuous median crest- 



