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differences that exist between the dr}- forest and the cloud forest. The 

 l^rincipal dift'erence in habits between the two species in the groups in this 

 region is in food habits, the Hzards being largely insectivorous, the snakes 

 mostly carnivorous. Certainly the food supply for lizards is much more 

 different in the cloud forest and in the dry forest than it is for the snakes. 



Taking into consideration the known altitudinal distribution and the 

 habits of the species, the conclusion seems warranted that an absence of 

 standing water and greater humidity and more shade above 2,200 feet" 

 may be important factors in limiting the downward and upward migration, 

 respectively, of the cloud forest and lowland amphibians, and that the 

 more open conditions below 2.200 feet are more favorable than those in 

 the wet forest for at least five of the lizards found below 2,200 feet, as 

 they occur above this altitude when clearings are made. 



It should not be inferred that the writer denies the influence of tem- 

 perature in limiting the vertical distribution of particular species in this 

 region. It is only meant that particular temperatures are not clearly respon- 

 sible for the zonal distribution. It is quite possible that when several spe- 

 cies are stopped at approximately the same place, in some cases a temper- 

 ature difference may be the cause, while with others other factors may be 

 operative. This view is quite in harmony with physiological data, and on 

 San Lorenzo other factors are probably operative, since the abrupt change 

 from desert to cloud forest is attended by changes in many environmental 

 conditions for animals. 



Rclofions of the Cloud Forest Faunas: The fact that, while the lizards 

 and amphibians of the cloud forest are limited in their downward range 

 in the moderately wet forest on the northwest slope of San Lorenzo, five 

 out of the eleven species not found below 2,200 feet are known to occur 

 elsewhere on the lowland, is more than evidence that temperature is not the 

 only controlling factor in the vertical distribution, but would seem to indi- 

 cate clearly that this fauna is or has been continuous with a lowland fauna 

 containing many of the species found on San Lorenzo only above 2.200 feet. 

 To obtain informatiftn on the origin of the cloud forest fauna, work was 

 done at Don Diego and a trip was made entirely around the range from 

 Riohacha to Fundacion. In the work on the east and south sides of the 

 range the lizards received principal attention, in the belief that being more 

 easily collected they would be most likely to yield dependable results in the 

 short time which could be devoted to the work. The distribution of the 

 species is summarized in the accompanying chart. 



From the chart it will be evident that a desert or dry forest extends 

 from Santa Marta to Riohacha on the west, south, and east sides of the 

 range, and that as far as the lizards are concerned it is the principal fauna 

 of the lowlands. Of a total fauna of twenty-four forms only nine have 

 not been taken at Santa Marta, where there is no heavy lowland forest. 

 Of the nine forms not taken at Santa Marta four are distinctly forest spe- 

 cies (Mabuya agilis, Tupinamhis nigropunctatus, Loxopholis riigiceps, and 

 Polychrns spnrreUi), and it is believed to be significant that these species 



'• Conditions unfavorable for the development of eggs laid on the land. 



