518 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [June 25, 



than it does the same part in the Totipalmates, where it is thicker 

 and shallower. 



The outer surface of the dentary is divided into an upper and 

 lower tract in Swans and Geese by a groove which, beginning near 

 the trace of the suture with the angular and surangular elements, 

 curves feebly downwards as it advances forward : Cyc/nus Ruppelii, 

 in this character, nearly repeats that in Odontopteryx. 



The upper beak-bone in Anatidce does not show the longitudinal 

 groove which impresses it in Odontopteryx. But this groove is 

 present in Sula and Phalacrocorax. It commences behind, in 

 these sea-birds, a little in advance of the outer end of the naso- 

 frontal suture, and extends straight forward, about midway between 

 the upper and lower borders of the upper beak, to near its pointed 

 termination. The groove (PI. XVI. figs. 1 & 2, g) has the same re- 

 lative position on the sides of the upper beak in Odontopteryx ; but it 

 begins below the fore part of the zygoma, and rises with a curve 

 convex upward, to midway between the upper and lower borders of 

 the maxilla, along which it then runs straight as far as that bone is 

 preserved. 



The upper part of the upper beak in Sula is broad and arched at its 

 base, the transverse convexity being more marked as the beak nar- 

 rows and advances. In Odontopteryx an upper tract is pinched off, 

 so to speak, from the sides, flattened above at first, and becoming 

 transversely convex as it narrows and advances, the sides of the 

 beak below this tract being transversely concave in a feeble degree 

 before attaining the groove ( g ). This upper median raised tract re- 

 calls the more strongly developed one in Procellaria, and suggests the 

 possibility of its having been prolonged, in Odontopteryx, to terminate 

 forward, as in Petrels, in the outer opening of the tubular nostrils ; 

 but the mutilation of the beak in the fossil leaves this point purely 

 conjectural; and in all other comparable characters of the skull the 

 resemblances are found with the LameUirostrals and Totipalmates, 

 not with the Longipennate sea-birds. 



Another character approximates the fossil to Sida ; there is no 

 trace of a mid notch at the fore part of the frontal, into which, in 

 Anser palustris, the end of the nasal branch of the premaxillary is 

 produced; the transverse fronto-nasal suture abruptly defines the 

 cranium from the beak in Odontopteryx, as in the Totipalmates. 

 But the transverse contraction of the interorbital part of the frontal 

 is more considerable in the fossil, and the hind part of the naso- 

 premaxillary tract is flatter, with other differences from the Gannets 

 and Cormorants already noticed. 



Thus Odontopteryx, independently of its teeth, shows, in the unique 

 fossil representing the genus, its distinctness from all known exist- 

 ing genera of birds. 



Of the species which have the bill armed with tooth-like pro- 

 cesses, the enumeration is easy. The true Falcons have the single 

 " tooth " on each side of the upper jaw; a like armature of the beak 

 of the Butcher birds has suggested the term " dentirostres " for the 

 tribe of Passerines including the Laniidce. The male of one genus 



