206 Proceedings of the Royal Physical Society. 



variety of surroundinsis, and differins; from each other more 

 or less in their habits, should have each evolved crests inde- 

 pendently. We may, therefore, conclude that the possession 

 of this character dates back at least as far as the differentia- 

 tion that gave rise to the genus. But several allied genera, 

 united into one sub-family by certain common points of 

 structure, agree also in this particular feature, and are crested 

 on the same type. For example, taking the Herpeto- 

 THERIN^, we find that all the genera, Spilornis, Uutriorchis, 

 Helotarsus, etc., agree in possessing a great development of 

 broad, round-ended, occipital feathers ; although the several 

 genera composing that sub-family are distributed over the 

 greater part of Huxley's Notogiea. Then again, to take 

 another example, all four genera ranged under the Thrasae- 

 TiN^ are crested in one way or another. Even in the 

 Aquiltn^e seven out of the nine sub-genera ranged under 

 this sub-family are crested, and of one of the remaining 

 genera, Aquila itself, a single species, A. desmursii, possesses 

 a distinct occipital crest. 



These facts appear to me quite to warrant us in regarding 

 the feature under notice as one of great antiquity, and as 

 having been transmitted, with but little modification, from 

 the parent stock of each of the sub-families whose members 

 now possess such decorations. Where did those crested 

 ancestors originate ? If we study the geographical distribution 

 of tlie existing crested genera, it seems to me that we can 

 obtain some kind of reply. We will take the various groups 

 seriatim, noting whether they contain crested forms or not ; 

 and, if they do, in what zoological provinces these particular 

 forms occur: — Falconintr, no crested forms. AcciPiTKiNiE 

 — Lophospizias, alone : Indian Eegion. Buteoninti^., none. 

 MiLViNiE — Baza, alone : Oriental Eegion and N. Australia, 

 S.-W. Africa. CniciN^, none. PEKNIDiE^ — Macha^ramphMs : 

 S.-W. Africa, ^Madagascar, and ]\Ialacca. Pernis (one species 

 of): Indian Eegion. Gymnogenin.^. — Pohjhoroides: Ethiopian 

 Eegion and Madagascar. Herpetotherin^. — Herpetotheres : 



^ The Honey Buzzards and their allies appear to me to be aberrant forms, 

 and (juite entitled to be regarded as the existing representatives of a nearly 

 extinct family. 



