442 STEUCTURE AND CLASSIFICATION OF BIRDS 



there is traceable a gradual series of modifications. In the 

 storks the accessory femorocaudal is always absent, and in 

 some the ambiens and femorocaudal also ; in the Ardeidse both 

 ambiens and accessory femorocaudal are gone, and the 

 modification of these leg muscles culminates in the aberrant 

 Cancroma, where the formula is merely XY — . In the 

 Plataleidse (as in Tantalus) there are just faint traces of the 

 basipterygoid processes, missing elsewhere in the group. 

 The ibises are schizorhinal, and in Platalea the ends of the 

 nasal grooves are rounded, thus tending towards the holo- 

 rhinal, while the lower part of the bony nostril is wider than 

 the upper, appearing thus to show a commencing occlusion 

 of the schizorhinal nostril into a holorhinal one ; in Ardea 

 cinerea a faint trace of a former schizorhinal condition is 

 seen in a slight groove which runs back from the end of the 

 holorhinal nostril, as in Chunga (see p. 144). The schizo- 

 rhinal condition, as has been before pointed out, is probably 

 the more archaic. Finally the Plataleidse have, according 

 to Mitchell, the most primitive form of gut among the 

 Herodiones. Significant points of likeness between the 

 Plataleidse and Grues are not wanting ; the occipital foramina 

 and the impressions of the supra-orbital glands were among 

 the facts that led Fobbes to associate them together. The 

 convoluted windpipe is common to Platalea, Tantalus, and 

 Grus. Both Platalea and Grus have the complete muscle 

 formula and schizorhinal nostrils. 



It has been often asserted that there are likenesses 

 between the Herodiones and the accipitrine birds. This 

 largely reduces itself to a comparison between the Herodione& 

 on the one hand and the Cathartidse and Serpentarius on 

 the other ; for if the two latter forms of accipitrine birds are 

 rightly so placed the falcons must, on account of the various 

 reductions in their structure, be derived from some form near 

 to these, and cannot be their ancestors. There are two at 

 first sight rather striking likenesses between the Herodiones 

 and these lower accipitrines. Gadow has commented upon 

 resemblances in the lie of the intestines, and Mitchell has 

 still further emphasised this likeness. In both groups (the 



