Todd-Caeeiker : Birds of Santa Marta Region, Colombia. 79 



confined to the region Phaethornis longirostris susurrus, Attila par- 

 virostris, and Pheugopedius lietus are perhaps the most isolated from 

 their congeners, and when more is known of certain other forms on 



Fig. 4. Range of Pheugopedius latus (i), a species peculiar to the Santa 

 Marta Region, and of its probable antecedent, P. rutilus (2). 



the list they may likewise prove to be actually as well as apparently 

 isolated. (See Figures 4 and 5.) In nearly every case the derivation 

 of these peculiar forms is evident, and will be considered more in 

 detail beyond, under the head (jf the several species in question. 



While we are discussing the peculiarities of the Santa Marta Trop- 

 ical Zone fauna it may be well to call attention to its lacuncz, which 

 are fully as marked as its positive characteristics. It is of course pos- 

 sible that further intensive field-work will close some of these lacunae, 

 but on the other hand it is not conceivable that the apparent ab- 

 sence of so many genera and superspecific groups from the region 

 is not without significance. Not to go beyond such forms as are known 

 to have a comparatively extensive range in the Tropical Zone, occur- 

 ring on both sides of the Santa Marta region, it is difficult to account 

 for the apparent absence in the latter of any representative of the 

 Columbine genus Zenaida, of such well-known and widely distributed 

 aquatic forms as Gallinula, Heliornis, Colymbus, Podilymhus; ^Ryn- 



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