170 STRUCTURE AND CLASSIFICATION OF BIRDS 



to the Upupidse than to any other groups except the coUes 

 and Alcedinidse ; we may therefore unite them. 



Finally as to the passerines. It is not possible to place 

 them very definitely nearer to one than to another of the 

 groups enumerated. They differ at the lowest in four 

 characters from any. They are, perhaps, furthest away from 

 the Bucerotidae ; the two groups, in fact, are typical members 

 each of them of the piciform and passeriform birds of 

 Gaerod. Their leanings are perhaps to the Cypselidse and 

 to the Pici. 



These conclusions may be tabulated as follows : — 



Group A. — Aftershaft present ; fifth remex always present. 

 Muscle formula, AXY. Expansor secundariorum' present. 

 Desmognathous. Vomer present. 



This group contains the families Coraciidae, Meropidss, 

 Todidse, Galbulidse, and Momotidae. 



By both Gadow and Fuebringbe the Galbulidse are 

 placed nearer to the Bucconidse, and by inference to the Pici 

 (Picidse, Ehamphastidse, andCapitonidse). They differ, how -- 

 ever, from these by the presence of the expansor secundario- 

 rum, which is so rarely present among anomalogonatous 

 birds that when present it seems to be of special importance. 

 The most salient point of agreement between these latter 

 birds is the form of the deep flexor tendons. But the 

 Bucconidse are so little known that they may be found to 

 differ more than is at present suspected from the Pici. In 

 this case it may be desirable to separate both Galbulidse and 

 Bucconidae from the group with which I now associate them 

 and place them nearer together. Of the group as at present 

 constituted the Todidse have perhaps the most claims to be 

 regarded as the most primitive forms. They have a feathered 

 oil gland and long caeca, which two characters do not coincide 

 in any other of the families now under consideration. 



The next group, that of the Pici, may be thus defined :— 



Group B. — Fifth remex always present ; deep flexor 

 tendon of type VT. Expansor secundariorum absent. 

 CucuUaris propatagiahs present. No caeca. Vomer 

 present. 



