96 Mr. H. Seebohm on the 



8. The maxillo-palatines^ like those of the PalamedeaSj are 

 thin plates fused with each other across the palate for their 

 entire length. 



The combination of the 3rd and 4th characters is abso- 

 lutely diagnostic, and within the order the combination of 

 the 2nd, 4th, and 6th characters is equally diagnostic. 



In their geographical distribution they are almost cos- 

 mopolitan, and comprise two families, many genera, and 

 about 180 species. They are very closely related to the 

 Palaraedeae, and are probably not distantly allied to the 

 Phoenicopteri. 



The Cygnidse differ so widely in their osteological cha- 

 racters from the Anatidse that it is impossible to regard 

 them as part of the same family. The number of cervical 

 and cervico-dorsal vertebrae varies in the Cygnidse from 23 

 to 25. No other living birds are known to possess so many : 

 in the Anatidae and in the Platalese and Herodiones their 

 number varies from 16 to 19. The Cygnidfe further differ 

 from the Anatidse in having, when adult, no lateral occipital 

 fontanelles* and in having very few dorsal vertebrae furnished 

 with ventral processes. 



The Phoenicopteridse agree with the Anatidse in the two 

 first-mentioned of these characters, and with the Cygnidse in 

 the third, but they differ from both in other important 

 characters. 



Phcenicopteri. 

 The Flamingoes are intermediate between the Anseres and 

 the Herodiones, and appear to be closely related to the 

 Palamedese and the Plataleae. They possess the following 

 characters : — 



1. They are heterocoelous in the articulation of their dorsal 

 vertebrae. 



2. They are holorhinal in the bifurcation of their nasals. 



3. They have only one xiphoid process on each side of the 

 median process of the posterior margin of the sternum. 



* This is a very unsafe character to rely upon, as young birds of many 

 .«(pecies of Swans show large lateral occipital fontanelles, and in very old 

 Ducks thev are sometimes ossified. 



