302 Alexander G. Ruthven, 



opMs sauritus proximiis was found in small niimbers about the ponds, 

 but it was quite aquatic, and is placed in the pond habitat. 



The meagreness of the fauna of the savannah grassland is shown 

 more strikingly when the scarcity of individuals is considered with 

 the small number of species. The habitat was worked carefully, and 

 everywhere specimens were very rare except of the three species 

 of amphibians noted, and these were far from common anywhere 

 even on the immediate shores of ponds. 



The mammals and birds of the savannah grassland are also 

 apparently few in individuals and species. We observed no species 

 of these groups to be abundant in this habitat with the exception 

 of the Stone Curlew, Oedicnemus Ustriatus (Wagler), and only three 

 that could be considered characteristic. The stone curlew and a 

 meadow lark were observed nowhere eise, the former rather abun- 

 dantly, and a pocket gopher was found here but more commonly in 

 the lowland Clearings. 



The fact that the savannah grassland supports no characteristic 

 vertebrate fauna seems to the writer to support very strongly the 

 conclusion of 0. F. Cook i) (for Central America) that such grass- 

 land areas represent old artifical Clearings. It is known that the 

 region about Cuatotolapam was many years ago utilized as a cattle 

 ranch by the Spaniards, and at the present time thousands of cattle 

 are pastured there. The original Clearing may have been done by 

 the cattlemen or the latter may have found the area already, at 

 least partially, cleared by the methods of agriculture practiced by 

 the natives (cf. Cook). But the continued exclusion of the trees 

 and the development of the grassland associations may be attributed 

 to the coustant grazing. 



The savannah forests and thickets also have a scanty amphibian- 

 reptile fauna, but the latter is richer in species and individuals 

 than that of the grassland. The only forms that were not found 

 elsewhere are Leptodeira personata, one specimen of which was seen 

 (in a thicket), and CnemidopJiorus deppei. Ameiva undulata, Sceloperus 

 variabilis, Ctenosaura acantkura completa and Anolis sallaei are rather 

 characteristic of this habitat, but they were also found in partial 

 Clearings on low ground. The other forms observed here were only 

 seen a very few times. The ponds on the savannah also have but 

 a small fauna. The amphibians, Leptodadyhis albüabris, L. caliginosus, 



1) in: U. S. Dept. Agricult. Bureau of Plant Industry, Bull. 145. 



