^"'iVl^^l SHUFELDT, Skeleton of ll'edf/e- tailed Eagle. 297 



Such individual differences in the skulls, or, indeed, in any 

 part of the skeleton of birds (or other vertebrates) of the same 

 species, is a matter I have frequently invited attention to in my 

 osteological papers ; yet many writers on avian osteology, in de- 

 scribing the skeleton of some ])articular bird, present us with 

 tabulated measurements of bones, in a way that leads one to 

 belie\e that those same measurements will be found to obtain 

 in all aduFt specimens of the same species of bird. This is by 

 no means true, and will hold no better with birds than it will 

 with our own species ; we all know how the skull and other 

 bones of the skeleton in Homo vary in such particulars. Some- 

 times, in fact, very frequently, such dift'erences may either be 

 due to sex or to the age of the individual ; but not always. Take 

 Eagles, for example, we may find that the skulls of two adult 

 males of the same clutch, hatched at the same time and having 

 the same parents, present, when both become adult, very per- 

 ceptible differences in any of the bones of their skeletons, and 

 especially in the skulls. Among not a few others, a good ex- 

 ample of this may be noted in the case of these Wedge-tailed 

 Eagles. Mr. Scott, in the skull of that species described by 

 him (see antea) says: "The extreme length of the skull between 

 verticals is 122 mm." I find the extreme length to be 124 mm. 

 in the skull sent me by the Melbourne Aluseum, and in the skull 

 from Captain White it is 120.5 mm. This may be a sexual dif- 

 ference — a point I cannot pass upon with certainty, for the 

 reason that th.e sexes of these two birds are not known to me ; 

 evidently they were. both adult. 



Similar dift'erences or even greater ones, are seen to exist in 

 the cases of the interorbital fenestrce — strikingly so in "the depth 

 of the beak" and other measurements. This is not only true of 

 measurements, it also applies to characters ; and Mr. Scott 

 states, in the case of the Wedge-tailed Eagle examined, 

 that "ui)on the vertex of the skull there is a median 

 depression similar to that found in the Chestnut-faced 

 Owl, but less strongly marked." This is quite true of 

 the skull of the Eagle from Captain White ; but no 

 such furrow or depression exists in the skull of the Eagle 

 from the Melbourne j^luseum, where the medium fronto-parietal 

 region is quite flat or even a trifle full. 



One example more, and we will again pass to the considera- 

 tion of the skull. Apart from similar differences in the measure- 

 ments of the sternum, Mr. Scott says of the sternum of the 

 Wedge-tailed Eagle that "the sternum of this Eagle, unlike that 

 of the Indian Vulture, has no posterior fontanelles, and the 

 notching is also slight. "j Now there are no posterior sternal 

 foramina in the sternum of the Eagle from the Melbourne 

 Museum, and no notching whatever to the straight posterior 



t There is no paging to Mr. Scott's brochure, so the pagination cannot 

 be given in quoting him. R.W.S. 



