336 STRUCTURE AND CLASSIFICATION OF BIRDS 



on account of the fact that they are in several respects much 

 altered by modification from their allies. They show 

 evidence of degeneration in the loss of the oil gland, in the 

 occasional loss of one of the two carotids, in the absence of 

 the biceps slip, and in the reduced muscle formula of the 

 leg. Gaeeod associated with the bustards the Cariamidse, 

 (Edicnemidse, Serpentarius, and possibly Phcenicopterus. 

 There is, in my opinion, more to be said in favour of 

 associating the first two families with the bustards than the 

 last two. But, as I have pointed out elsewhere, Serpentarius 

 shows more than one hint of a crane-like origin. As to the 

 first two groups, they agree with the bustards in the muscle 

 formula BXY, in the holorhinal nostrils, in the absence of the 

 biceps slip {Cariama), the absence of basipterygoid processes, 

 the absence or feeble development of intrinsic muscles to the 

 syrinx ; the oil gland too, absent in the bustards, is nude in the 

 cariamas, and thus shows a commencing reduction. But these 

 various cases of reduction cannot be held to be necessarily 

 indications of relationship. I should, however, lay some stress 

 upon the holorhinal nostrils, the leg muscles, and the syrinx ; 

 in this case the same conclusion as that advanced by 

 FtJEBEiNGER is arrived at, viz. that the Otides come nearest 

 to the (Edicnemidse. The very difficulty of associating the 

 Otides with either gruif orm or charadriiform birds is evidence 

 of the common descent of all three divisions of the class. 



LIMICOL^ ' 



Definition. — Oil gland feathered. Aftersiaft present. Aquincubital. 

 Skull schizognathous. Both, carotids present. Cseoa nearly 

 always large. Ambiens^ always present. Biceps slip to patagium 

 nearly always present. 



This is a large group of birds which are cosmopolitan in 

 range and embrace a variety of types, which may perhaps 

 be arranged in six families. The type family is that of the 



' Seebohm, The Geographical Distribution of the Charadriidce, &o., London, 

 1887. A monograph of all the species (exol. gulls). 



^ Bhynchops is alone exceplional in having no ambiens. 



