■27-2 STRUCTURE AND CLASSIFICATION OF BIRDS 



the Musophagi, which are, similarly to the parrots, on the 

 border line between the AnomalogonatsB and higher birds. 

 It is noteworthy also that of the Anomalogonatse which 

 present a catapophysial canal (found at any rate in one 

 parrot) it is the Piei and the passerine alone. But while it 

 is not so difl&cult to point . out likenesses to the Anomalo- 

 gonatse it is much harder to indicate resemblances to any 

 of the higher groups of birds. It must be held, in my opinion, 

 that they have emerged from a low anomalogonatous stock 

 at a time not far removed from that at which the Cuculi and 

 Musophagi also emerged, but that there is not a common 

 starting point of the three groups. 



CUCULI 



Definition. — Feet zygodaotyle by reversion of fourth toe. Skull 

 desmognathous, without basipterygoid processes.' Oil gland 

 nude. Quintooubital. Two carotids. Ceeoa longisb. Ambiens , 

 present. 



The family which is defined by the above characters is a 

 large one, comprising, according to the recent catalogue of 

 Captain Shelley, 165 species, which are distributed by 

 that ornithologist into forty-two genera. 



The family is almost world-wide in range, being most 

 abundant, however, in the tropics. Correlated with its 

 numerous genera and species and wide range we find a 

 certain amount of structural variation in the family, which 

 permits of its division into several subfamilies, concerning 

 the number and extent o'f which there is some divergence of 

 opinion. It may be convenient, however, to consider the 

 general anatomy of the family before dealing with its major 

 subdivisions. 



Apart from the facts used in the definition of the family 

 the cuckoos are characterised by the absence of, or the 

 presence of only a rudimentary, aftershaft to the contour 

 feathers. The number of rectrices is not, as was stated by 

 NiTZSCH, constantly ten ; for in Saurothera, Guira, and Groto- 

 ' Well-marked rudiments in Rhinoeoccyx and Eudynamis. 



