294 ON THE ANATOMY OF PHAETHON. [Feb. 16, 



would have to be ignominiously expelled from the Order. This 

 catastrophe is averted by Frer/ata, the skull of which, as will have 

 been gathered from the foregoing remarks, serves to link Phaethon 

 ■with the Cormorants, Graunets, and Pelicans. 



The Stegauopodes are always spoken of as ]Jesmognathous bii'ds. 

 But can Phaethon, be accurately termed a desmoguathous bird ? 

 This altogether depends upon the definition of the term desrao- 

 gnathous. Huxley, its inventor, defined ' the condition of Desmo- 

 gnathism as follows : — " In these birds the vomer is often either 

 abortive, or so small that it disappears from the skeleton. When 

 it exists it is always slender and tapers to a point anteriorly. The 

 maxillo-palatines are united across the middle line, either directly 

 or by the intermediation of ossifications in the nasal septum." 



As to the vomer of Phaethon, it is pointed in front, as is that of 

 most ychizognathous birds ; this character does not distinguish the 

 Schizognathse. But, as already mentioned, it diverges behind into 

 its two component halves, in a way that is unusual among 

 Desmoguathous birds. It occurs, however, in the Herons (not in 

 Scojms), which are admittedly allies of the Stegauopodes. In 

 8chizognathous birds, on the other hand, this bone is commonly 

 divided behind. This part of the palate in Phaethon is in fact 

 remarkably like that of a Grebe {cf. figs. 3 and 5). Nor does the 

 resemblance cease liere. Phaethon is really no more desmognathous 

 than is ^chmophoriis, if we apply the term as Huxley applied it ; for 

 the maxillo-palatines in both are widely apart, the vomer lying be- 

 tween them. In front of the maxillo-palatines, however, in Phaethon 

 the bony palate forms a continuous platform. If this constitutes 

 desmognathism (which it does not, be it observed, according to the 

 definition of Huxley), then Coracias, Eanji^tomus, Jacamerops, etc., 

 in which birds there is a considerable \acuity in front of the con- 

 joined maxillo-palatines, are not desmognathous ; while the skulls 

 of Gecinus virulis and Dcndrocopus major (at most only just separ- 

 able generically) must in that event be referred to different 

 categories ; since in tlie former there is a palatal platform, and 

 in the latter not. 



In Pelecamis and Phalacrocora^r, Huxley has figured fused 

 maxillo-palatiues. These consist in the latter genus, in Plotus, 

 and in Sula of a thick mass of bone running upwards towards 

 the roof of the skull. Their direction is quite different from the 

 borizontallydisposed maxillo-palatines of Phaethon, The conditions 

 observable in the base of the skull of Fregata appear to me to clear 

 up this somewhat puzzling discrepancy. In Frer/ata (see fig. 4, 

 p. 293), we have loth the horizontal maxilh-palatines of Phaethon, 

 separated from each other in the middle line as in that genus, 

 and the obliqueh/ ruiinin;/ '■'■ inad'illo-palailws^' of Phalacrocorax. 

 As co-existence undoubtedly disproves homology, it seems to 

 follow that true maxillo-palatines, comparable to those of other 

 birds, are wanting in Sula and Phalacrocoracc : and if we are to 



I " On the Classification of Birds &c.," P. Z. S. 1867, p. 435. 



