MR. W. K. PARKER ON THE OSTEOLOGY OF BAL^NICEPS REX. 



275 



Balaeniceps and Adjutant. There is only a general class-resemblance between this part 

 of the Pelican's skull and that of the Balseniceps. 



The occipital cincture in the Boat-bill {Cancroma) is intermediate between that of the 

 Heron and the Balseniceps ; the crests marking its boundary are thicker, but not more 

 distinct than in the Heron ; in Balseniceps these ridges are fainter, at least in the skull 

 of this scarcely mature captive. 



Upper Cranial Surface. (PI. LXV. fig. 6.) 



The upper surface of the skull in this strangely interesting bird is formed (as in the 

 rest of its class) principally by the parietals (figs. 1 & 6, ^) behind, and the principal 

 frontals anteriorly. The lacrymals (figs. 1 & 6, Z) generally assist the principal or sphe- 

 noido-frontals (figs. 1 & 6, fr) in front ; but in the Balaeniceps and a few other birds 

 these bones are facial, being anchylosed to the nasals (figs. 1 & 6, n), or ethmoid o-frontals 

 of Goodsir, and intermaxillaries. The parietal region is eked out laterally in all birds 

 by the squamosals (PI. LXV. figs. 1 , 3, 6, & 7, sq) — the temporals of Cuvier, and the 

 mastoids of Owen, but incontestably shown to be the homologues of the mammalian 

 squamosals in the masterly Croonian Lecture of Professor Huxley, p. 13. 



The only birds having a broad, flat, smooth cranial surface at all comparable to that 

 of the Baleeniceps are the Maccaws {Ara) ; although some of the Totipalmatse make some 

 approach to it, e. g. the Pelican and the Gannet. 



In Cancroma the distance between the orbits is proportionally much less, and the 

 general surface, although smooth, is more irregular, whilst in the Adjutant it is convex 

 and rough. In the Heron, the upper part of the skull is as polished and smooth as that 

 of the Balaeniceps ; but its shape is very different, its length being very great in propor- 

 tion to its breadth. The relative proportions of the upper part of the Balseniceps will 

 be best shown by a few comparative measurements, the width and length being taken 

 at the following points. 



Measurements of Crania. 



First measurement, — across the eranio-facial hinge. 

 Second measurement, — across the middle of the orbital margins. 

 Third measurement, — across the post-frontal processes. 

 Fourth measurement, — entire sagittal line of the skull proper. 



1. Adjutant, Leptoptilus . . . 



2. Wliale-bird, Balceniceps rex . 



3. Boat-bill, Cancroma cochlearia 



4. Goatsucker, Podargus humeralis 



5. Grey Heron, Ardea cinerea . 



6. Hornbill, Buceros hicornis . 



7. Maccaw, Ara ararauna 



8. Pelican, Pelecanus onocrotalus 



