468 STRUCTURE AND CLASSIFICATION OF BIRDS 



which is pecuhar in that posteriorly the lacrymal is free 

 from the orbital wall, but is fused with a process of the 

 frontal at the anterior end of the supra-orbital impression, 

 leaving (as in Chionis and some other birds) a foramen.' In 

 Cereopsis the descending process of the lacrymal curves back- 

 wards and comes near to the zygoma ; ^ the junction is 

 completely effected, and there is ankylosis, in Detidrocygna. 



The ectethmoids of the Anseres are often largely deficient 

 as ossifications ; when present they are thin-walled bubble- 

 Hke structures, coming into relation with the lacrymals. 

 The interorbital septum is generally very complete ; but it 

 is largely vacuolate in Mergus and Biziura. 



The following table shows the number of cervical 

 vertebrcB and the condition of the hsemapophyses and 

 catapophyses in a series of anserine birds : — 



^ Fused to form a solid bifid ' hsemapophysis,' as in some other birds. 

 " They are rudimentary and do not mount upon the hypapophysis. 



As a possible appendix to the Anseres must be mentioned 

 three or four species of an extinct genus of birds, Gastornis, 

 flightless and larger than an ostrich.. It has been found 

 only in Europe and from Eocene beds. It is placed among 

 the ' ratites ' by Ltdbkkee and some others ; this is largely 

 on account of the coracoid, which is imperfect above, and 

 appeared to Lemoinb and others as probably 'platycora- 

 coidal.' EtfBBBiNGBR, however, considers that the tuberosity 



' This is figured by Owen in his paper on Cnemiornis, Tr. Z. S. ix. pi. 35^ 

 fig. 8. 



' Sometimegjoining. Cf. Owen, loc. cit. pi. 35, fig. 6. 



