Avifauna of Central America. 7G3 



less important factor, the distribution in time. But even 

 when the evidence from these two sources has been duly 

 weighed, no satisfactory conclusion can be reached without 

 an appeal to the evidence afforded by the genetic affinities of 

 the particular group under discussion. The case of the 

 New World Coraciiformes affords a useful illustration of 

 this. The Trogons may well serve as a starting-point. 

 The centre of dispersal of these bii'ds seems estai)lished 

 beyond dispute. They represent an extremely ancient and 

 somewhat isolated group, displaying affinities, on the one 

 hand, with the Caprimulgi and Cypseli (including the 

 Troehili) and the Colli, and, on the other, though more 

 remotely, with the Momotidre. The majority of living 

 species occur in Central and South America ; hut two 

 occur in Africa and ten in the Indo-AIalayan region. The 

 Trochilidse are exclusively New World types ; so also are 

 the Momotidse, which, it is to be remarked, are the most 

 aberrant members of the Coraciiformes. The only other 

 representatives of this family which have found their way 

 into the New World are the members of the genus Ceryle 

 among the Kingfishers, which have become cosmopolitan. 

 It is worth comment that neither Bee-eaters, Hoopoes, nor 

 Hornbills have found their way into the New World, 

 though the two last-named occur with the remains of 

 Trogons in the Miocene of France, Since the Trochilidse 

 are undoubtedly but highly-specialized Cypselidse, it is 

 possible that they may liave arisen within the limits of 

 the American continent. 



That the Picidge and Capitonidse are extremely ancient 

 types there can be no doubt. Fossil remains of the first- 

 named, it has already been remarked, have been found 

 in the Eocene both of France and Wyoming, showing 

 that already in this remote era the family had spread over 

 an enormous area. To-day its members are encountered in 

 every quarter of the globe, save Madagascar, Australia, and 

 Polynesia. The Capitonidye are unquestionably nearly 

 related to the Picid?e, and must date almost, if not quite, 

 as far back in time. Apparently less able than the Wood- 



