82 Annals of the Carnegie Museum. 



ated on the south slope of the Sierra Nevada at an elevation of 6,700 

 feet, and therefore well within the normal altitudinal limits of the 

 Subtropical Zone. Much of the surrounding- country is open, grassy 

 plains, and here we find a Meadowlark, Sturnella magna paralios, 

 which is elsewhere unknown except at much lower altitudes in Colom- 

 bia and Venezuela. In the scrub growth are also found such char- 

 acteristic Tropical Zone forms as Piaya columbiana, Saucerottia 

 saucerottei warscewiczi, Antrostomus ritfus rufus, Sayornis latirostris 

 fumigatus, Tyrannus melancholicus chloronotus, Muscivora tyrannus, 

 and Mimas gilvus melanopterus, together with Temperate Zone forms 

 such as Orodynastes striaticollis striatic ollis, Semimerula cacozela, 

 Brachyspiza capensis peruviana, and Spinas spinescens capitaneus. 

 Subtropical Zone forms occur here also, but are confined to their ap- 

 propriate habitat. Hence we infer that the Tropical and Temperate 

 Zone forms are here a recent infusion, brought in by local conditions. 

 The general character of the vegetation of the Subtropical Zone 

 has already been fully described under Ecological Conditions. It has 

 been traced across the northern and western flanks of the mountain 

 system of this region as a continuous belt, but we do not know whether 

 or not it keeps on around the southern and eastern slopes without in- 

 terruption, since these sections have not been so thoroughly investi- 

 gated. What information we have on the distribution of forests in 

 these parts would lead us to believe that the Subtropical Zone is here 

 discontinuous, perhaps as a result of deforestation in recent times. 

 Although a few Subtropical forms habitually drop down into the Pied- 

 mont belt of the Tropical, the boundary between the two zones is suf- 

 ficiently well defined by the cloud-level. On the north slope of the 

 Sierra Nevada, however, due undoubtedly to the unusually low- (and 

 possibly variable) altitude of atmospheric condensation (2,000 feet), 

 numerous Tropical Zone forms range above this level, and there is 

 more or less overlapping of the two zones — a very unusual condition. 

 When we come to determine the upper limit of the Subtropical Zone 

 in this same region, we find a similar and even more marked over- 

 lapping between this zone on the one hand and the Temperate on the 

 other. Few typical Subtropical Zone birds are known to range above 

 9,000 feet in this region, and some do not go above 6,500 feet, while 

 several characteristic species of the Temperate Zone, on the other hand, 

 are known to drop down as low as 5,000 feet. On the San Lorenzo, 



