CUCULI 281 



a. Ventral tract occupying whole of space between 

 jaws. 



Old World. 



Con a (?) 



b. Ventral tract only occupying median region. 



Geococcyx \ 

 Crotopha'ga hNew World. 

 Guira 



The question of the affinities of the cuckoos is a difficult 

 one. 



By GADOW they are placed nearest to the Musophagi and 

 next nearest to the Psittaci. FUEBEINGEE'S views do not 

 greatly differ. There seems to be no doubt that these birds 

 are an archaic group not far from the point where the Ano- 

 malogonatae and Homalogonata? of GAEEOD diverge. They 

 are, like the Musophagi, quintocubital ; their intestines are 

 simple ; and they have the complete muscle formula (B being 

 in some forms absent). These characters are found in others 

 among the more primitive of the higher birds. 



The likenesses wiiich the cuckoos show to the Pico-Pas- 

 seres are mainly in the structure of the foot, in the simple 

 character of the tendons of the patagium, and the marked 

 resemblance in the syrinx to that of the Caprimulgi, and in a 

 less degree to the Striges. As has been pointed out, precisely 

 the same series of modifications between the extreme bron- 

 chial syrinx of Crotophaga and the purely tracheo-bronchial 

 syrinx of Cucidus are to be seen among the Caprimulgi. The 

 syrinx is really the only salient point in the anatomy of 

 the group that can be laid hold of for purposes of com- 

 parison, and, considering the dissimilarities in the voice and 

 habits of cuckoos and goatsuckers, it is particular])' note- 

 worthy. 



As to fossil cuckoos, the two most interesting facts are, 

 perhaps, the occurrence of Centropus and Phoenicopliaes ' in 



1 See MILNE-EDWARDS in Comptes Rendus for 1894. 



