52 CALIFORNIA ACADEMY OF SCIENCES. [PROC. 30 SER. 



saddle was one of their camping grounds. The specimens 

 from the earthy blocks show a free effervescence with dilute 

 acid, and contain in places rough, free, calcite crystals, 

 several millimeters in diameter. 



The lower slopes of the andesite in the Little Harbor 

 region, up to an altitude of six or seven hundred feet, are 

 everywhere strewn with rolled pebbles of andesite, por- 

 phyrite, and quartzite. Near the northern border of these 

 lower levels there are two small deposits of white, earthy 

 material. Along the southern border, on the ridge adjoin- 

 ing Middle Ranch Canon, there is a considerable deposit of 

 sandstone and conglomerate, and a little above this on the 

 same slope another deposit of the earthy material. All the 

 specimens of the latter rock wherever found effervesce 

 freely with dilute acid. A very few rough shell casts were 

 found in one of the areas of the earthy rock. The rock 

 powder under the microscope showed no organic remains. 

 The bulk of the powder gives the high polarization colors 

 of calcite. Some of the specimens contain occasional small 

 pebbles. In the coarser deposits there are all gradations, 

 from conglomerate, with pebbles averaging one-half an 

 inch in diameter, to a fine-grained, yellowish, micaceous 

 sandstone. None of these effervesce with acids. A search 

 for fossils revealed a few indeterminable shell-casts. These 

 deposits of sandstone and conglomerate are in general 

 thin, though at one point they reach a thickness of about 

 fifteen feet. 



D. BRECCIA. 



Beginning near the extreme southeastern point of the 

 island, and extending along the coast to the northward, is a 

 small area of quartzite breccia. As seen in the gulches it is, 

 in part at least, bedded, the beds varying in the coarseness 

 or fineness of their material. The coarser beds contain 

 occasional large blocks two feet or more in diameter, and, 

 rarely, reaching a length of several yards. The material 

 composing this breccia, so far as can be made out with a 

 lens, is wholly quartzite, except for occasional blocks and 



