INTRODUCTION. 



of the ambiens muscle and other leg muscles, and other inconstant minor 

 internal features. The author of these articles unfortunately died before he 

 was able to revise his early guesses as to the value of these items, and for the 

 last thirty years these have been accepted at an abnormal valuation. It 

 is now time to attempt a reasonable classification, but as previous schemes 

 have quoted the above it is important that they should be cited. 



In connection with the skull the palate was used by Huxley as a distin- 

 guishing character capable of differentiating groups of birds accurately. 

 He indicated four styles of formation to which he applied the names 

 dromseognathous, desmognathous, schizognathous and segithognathous. 

 Parker studied the matter more fully and added a fifth, saurognathous, at 

 the same time putting on record many facts indicating the spurious nature 

 of these divisions. As a matter of fact, aU the forms are produced by con- 

 vergence and divergence and cannot absolutely be used for the separation of 

 groups. It has already been stated that none of the divisions are really 

 satisfactory from the classificatory point of view by a professional anatomist, 

 but we consider they are valuable, after the external structure of the bird has 

 been well studied, in connection with other items. 



Garrod's great idea was the usage of the formation of the nasal bones, 

 the differences being termed holorhinal or schizorhinal. Here, again, there 

 was soon seen to be pseudo-holorhiny present, and consequently the terms 

 as originally proposed were proved to be futile. Once more, it will be found 

 that as a subsidiary item the distinctions may be accepted as confirmatory 

 evidence in many cases. 



Again, the presence or absence of basipterygoid processes was supposed 

 to be of importance, but the variability of their presence seems to relegate 

 these to a subordinate position. Regarded as indicating reptilian ancestry 

 they recur in the most specialised avian forms and are absent from admittedly 

 older groups, while in some groups they are present in the juvenile and absent 

 in the adult, and in very closely allied species do not occur at all. The absence 

 or presence of supraorbital grooves is sometimes quoted, but in a closely 

 allied series of species great variation may be seen. The form of the pterygoids 

 varies, but not much importance has been given to this character though it 

 appears just as worthy of usage as some of the other items cited by osteologists. 

 The quadrate is sometimes quoted, and it is a little variable so that it may 

 be used later in connection with other skeletal features. The lower jaw seems 

 so far to have been ignored but, we think, incorrectly. 



Owing to the exaggerated importance given to the palatal features the 

 rest of the skeleton has been comparatively neglected. When extraordinary 

 features were noted, through lack of knowledge these were unduly emphasised 

 or unfairly minimised. The variability of the sternum may prove just as 

 valuable as any feature of the skull when carefully studied. We have 

 recognised phylogenetic affinity in its variation in a few cases we have recently 

 studied ; the features sometimes quoted, the presence of spina externa and 

 interna, do not appear to have much significance. The forms of the vertebrae 



