200 Field Columbian Museum — Zoology, Vol. III. 



tains is to the west into the Pacific, and practically but one of the streams 

 has permanent connection with the ocean. 



"The higher parts of the mountains are of granite formation, the ' 

 ridges and peaks being composed of gigantic boulders produced by 

 weathering. Between these ridges occur level-floored valleys of consid- 

 erable extent. The southern and northern portions of the mountains are 

 largely composed of a hard, metamorphosed sandstone, and lack the 

 boulder formation so characteristic of the higher and central portions. 



"The forests of the plateau region are composed almost wholly of 

 yellow pine, Pinus jeffreyi, except on the higher elevations. This tree 

 ranges from 6,000 feet to the highest elevations and is almost every- 

 where the predominating one. In the lower parts of its range, 6,000 to 

 7,000 feet, it is restricted to the valleys, the ridges being bare of forest 

 growth, but above these elevations it is confined more to the hillsides 

 and ridges, the valleys being open and grassy. At lesser heights, 4,500 

 to 6,000 feet, the pinon pine, P. quadrifolia, is the only tree and forms 

 forests in some localities. The sugar pine, P. lambertiana, occurs spar- 

 ingly on the higher ridges, from 8,000 feet to the highest summits. The 

 two-leaved pine, P. murrayana, forms forests in the northern part at an 

 elevation of about 8,500 feet. A fir, Abies concolor, forms a limited por- 

 tion of the forests from 8,000 feet and above. The incense cedar, 

 Libocedrus decurrens, occurs about streams at 7,500 feet and on the hill- 

 sides at higher elevations. A few cypress, Cupressus arizonica, occur on 

 the highest elevations, but in such limited numbers as to be of slight 

 importance in the composition of the forests. A few oaks, Quercus 

 chrysolepis and Q. grisea, add to the forest growth at all elevations above 

 6,000 feet. In the higher elevations, mostly above 8,000 feet, the aspen, 

 Populus tremuloides, forms thickets and miniature forests about damp 

 meadows and stream-beds. 



"The chaparral clothes the hills and ridges at all elevations, except 

 in localities where the boulders are large and numerous. This growth 

 is made up chiefly of scrub-oaks, several species of Ceanothus, chamiso, 

 manzanita, Garrya, and at lower elevations, juniper. 



" The greater part of the mountain is in the Transition zone, as shown 

 by the distribution of the yellow pine. This zone approximately ex- 

 tends from 6,000 to 8,500 feet, or perhaps to the summit of the moun- 

 tains. The presence of the Canadian zone is somewhat doubtful, although 

 the occurrence of Abies and Populus tremuloides and of Sciurus d. mearnsi 

 give a touch of Canadian. The upper Sonoran zone is confined to the 

 region below 6,000 feet and limited to the slopes of the mountains down 

 to 4,000 feet, the whole zone being in a dense chaparral." 



"The topography of Ensenada," writes Mr. Heller, " is made up of 



