AmPIIIP.IANS AM) RliPTlLKS OF S-ANTA AIaRTA 4I 



were preserved with the specimens. It may at least be said for the data that 

 they are more detailed than those often used as the basis for conclusions 

 upon the environmental factors in distribution. 



Nature of the Materials: Although in a way a truism, it cannot too 

 often be reiterated that any attempt to summarize the distribution of the 

 terrestrial cold-blooded vertebrates must, to be convincing, take into account 

 the secretiveness, the apparent rareness, and the inconspicuousness of many 

 species which make collecting in these groups fortuitous in no small degree. 

 It is quite obvious that these attributes of the components of a fauna make 

 it difficult to determine with accuracy the limits of ranges, but it is too 

 often ignored in the practice of listing species of doubtful range by habitats, 

 zones, etc., suggested by the distribution of a part of the fauna, with the 

 result that the faunal areas receive support from records which should not 

 be considered adequate for the purpose. If the field work is carried on in 

 detail and over a considerable length of time, it is possible even in the 

 groups under consideration to reduce the species of unknown range to a 

 relatively small number, and it would seem to be the best practice to exclude 

 from summaries those forms so rare or secretive as to be represented in the 

 collections only by a few specimens from one place. The exclusion of rare 

 forniii can only lead to erroneous results when such species constitute a 

 considerable part of the fauna. 



Vertical Distribttfion: To obtain data on the distribution of the species 

 with altitude a detailed study of the fauna of the northwestern slope of 

 San Lorenzo was made. The conditions on this slope are very favorable 

 for the study of the vertical distribution of amphibians and reptiles. Located 

 in a region which supports a large fauna in these groups, rising rapidly 

 from sea-level to a height of 9,300 feet, and possessing great differences in 

 climate and vegetation within the space of a few miles, it is to be expected 

 that on this mountain the upper and lower limits of ranges will be rather 

 sharply defined and zonal distribution, if present, conspicuous. Moreover, 

 the region is accessible and as easily studied as such a region can be, since 

 trails have been cut to 8,300 feet and it is possible to obtain living quarters 

 at different elevations. 



It will be clear from Mr. Carriker's description of the region that the 

 vegetation in the San Lorenzo region changes from a desert flora to a 

 xerophytic forest fiora at about 100 feet, from a dry forest type to a wet 

 forest type at about 2,200 feet, the latter becoming a humid jungle type 

 above 4,500 feet. The greatest difference exists between the dry and wet 

 forests. The plains have, or evidently originally supported a considerable 

 growth of xerophytic trees, and above 2,200 feet, while the wet forest 

 becomes wetter with increased altitude, the change is gradual and the 

 flora is of about the same nature. At about 2,200 feet the change in the 

 type of forest on the ridges takes place within a short distance. There is 

 also at this point a marked change in the fall of the streams, so that it may 

 be said that above this altitude there are no ponds or pools, whereas lower 

 down these are often found in the broader valleys and on the plains. It is 

 possible that in larger valleys pools are to be found at somewhat higher 



