456 STRUCTURE AND CLASSIFICATION OF BIRDS 



but not fenestrate posteriorly. Occipital fontanelles are 

 absent. 



Though perhaps rightly placed in the neighbourhood of 

 the geese, it is obvious, from what has been said, that the 

 Palamedeida? are distinguished from them by many differ- 

 ences, of which the most important are perhaps 



(1) Continuous feathering. 



(2) Absence of biceps slip to patagium. 



(3) Peculiar form of intestinal casca. 



(4) Normal character of biceps cruris. 



(5) Emphysematous character of skin and breaking up of 

 cervical air sacs. 



On the other hand there is nothing in the skull which 

 forbids an association with the Anseres, and the windpipe, 

 with its two pairs of extrinsic muscles, is decidedly goose-like. 

 But it must be remembered that this feature is also found 

 among Galli, and in a few other forms. 



ANSERES ' 



Definition. Oil gland tufted. Aftershaft small or absent. Aquin- 

 cubital. Two carotids. Trachea with, two pairs of extrinsic 

 muscles. Casca long. Gall bladder present. Biceps slip present. 

 Glutseus maximus large. Muscle formula of leg, ABX + . Skull 

 desniogiiathous, with, basipterygoid facets. 



The swans, geese, ducks, and mergansers, which make up 

 this large assemblage of birds, are all aquatic, or semi-aquatic, 

 in habit, and in correspondence have webbed feet, with the 

 exception only of Anseranas. They are also for the most 

 part strong flyers, excepting only the living Tacliyeres cinereus 

 and the extinct Cuemiornis calcitrans. 



Tacliyeres cinereus, the ' steamer duck,' from the shores 

 of Patagonia, has been investigated by E. 0. CUNNINGHAM. 2 

 It does not appear from his memoir, which relates chiefly 

 to osteology, but in the course of which he describes and 



1 H. SEEBOHM, ' An Attempt to diagnose the Sub-Orders of the Ancient 

 Ardeo-Anserine Assemblage,' etc., Ibis, 1889, p. 92. 



2 ' On the Steamer Duck,' Tr. Z. S. vii. p. 493. 



