27-2 STRUCTURE AND CLASSIFICATION OF BIRDS 



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

 border line between the Anomalogonatae and higher birds. 

 It is noteworthy also that of the Anomalogonatae which 

 present a catapophysial canal (found at any rate in one 

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

 is not so difficult to point out likenesses to the Anomalo- 

 gonatae 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 

 Musophagl also emerged, but that there is not a common 

 starting point of the three groups. 



CUCULI 



Definition. Feet zygodactyle by reversion of fourth, toe. Skull 

 desmognathous, without basipterygoid processes. 1 Oil gland 

 nude. Quintocubital. Two carotids. Caeca longish. Ambiens 

 present. 



The family which is defined by the above characters is a 

 large one, comprising, according to the recent catalogue of 

 Captain SHELLFA", 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 of 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, aftersliaft to the contour 

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

 NITZSCH, constantly ten ; for in Saurothera, Guira, and Croto- 



' Well-marked rudiments in Rhinococcyx and Endynamis. 



