British Fossil Birds. 403 



specimens is mucli more in harmony with the estuarine con- 

 ditions which, from other lines of evidence, are inferred to 

 have prevailed in Sheppey during the early Eocene epoch, 

 than the view that these extinct birds were allied to such a 

 purely pelagic type as the Albatross. 



Another bird from the Sheppey Eocene seems to come 

 nearer to the existing Steganopodes than to any other living 

 forms, although clearly indicating a peculiar family. This 

 is the Odontopteryx toliapica of Owen, founded upon the 

 imperfect hinder portion of a skull described in the ' Quart. 

 Journ. Geol. Soc' for 1873. This skull, which is somewhat 

 larger than that of the Common Gannet, differs from that of 

 all other known birds in having the oral margins of both 

 upper and lower jaws armed with a number of pointed serra- 

 tions, some of which were larger than the others. In this 

 resj)ect it agrees exactly with certain Indian Chelonians, of 

 the genera Hardella and Batagur ; and it is evident that the 

 horny covering of the jaws must have had serrations fitting 

 on to those of the underlying bones, as is the case in the 

 Chelonians referred to. Certain existing members of the 

 Steganopodes, such as the Frigate-bird {Tachypeies) and the 

 Gannet [Sulci], approximate to Odontopteryx in having small 

 serrations on the horny margins of the jaws, but these serra- 

 tions are directed backwards instead of forwards. More im- 

 portant evidence of affinity is afforded by the deep grooves 

 which occur on the jaws of the fossil, and show that their 

 horny sheaths were composed of several distinct pieces, as is 

 the case in Tachypetes and Sula. The fossil genus was re- 

 garded by its describer as allied to the Anseres, and the 

 mandible was accordingly restored with a large recurved 

 postarticular process. But the skull differs from that of 

 all the Anseres in the shape of the quadrate, in which the 

 posterior surface is broad, and emarginate externally, while 

 the cup for the head of the quadrato-jugal is directed imme- 

 diately outwards.. Moreover, the depressed general contour 

 of the cranium, and apparently also the form of the lachry- 

 mals, are of the general type obtaining in the Steganopodes. 

 The fossil skull differs, however, from all the existing 



