Lawson "I 

 I'ai.acheJ 



The Berkeley Hills. 



391 



In the same bed have been found teeth of a species of Lept/s, 

 and the dentary bone of a species of Lacerta. In the clays asso- 

 ciated with the bed in which these bones were found, occur also 

 various molluscan forms, particularly species of Linineea, Helix and 

 Ancylus. In the' limestone beds of the Siestan formation, species 

 of Planorbis, Liminea, and Pisidium occur rather commonly. Some 

 years ago Cooper described* a few species of fossil mollusca from 

 a locality which is rather vaguely described, but which is supposed 

 to be the tunnel which was driven for water-supply purposes into 

 the Frowning Ridge escarpment at the base of the amygdaloidal 

 andesite at the head of Telegraph Canon. This tunnel is believed 

 to cut the Siestan beds, although this can not now be verified. 

 The forms mentioned by Cooper are: Anadonta nuttalliana, 

 Lea., var. lignitica, Limiuea contracosta, Cooper, and Planorbis 

 pabloanus, Cooper. 



Artesian Water. — Near the county road where it passes around 

 the head of Wildcat Canon a number of wells have been bored 

 through the Siestan clay, and a supply of artesian water of moderate 

 amount has been obtained. This of course indicates that the clay 

 stratum prevents the escape of the underground* water from the 

 more permeable strata beneath it. The water thus accumulates in 

 the lower beds until it establishes a hydrostatic level at a higher 

 altitude than the surface of the ground where the wells are, and 

 the latter, on piercing the impervious clay, permits the water to flow 

 freely at the surface under the head so established. 



Geomorphy Cojitrolled by Structure. — In thus tracing out the 

 distribution of the Siestan formation, we have practically encircled 

 a long lenticular or boat-shaped area of later volcanic rocks which 

 lie upon the Siestan beds, and have been subjected to the same 

 synclinal folding. These volcanic rocks form the topmost part of 

 the great stratigraphic sequence which we have been studying on 

 our line of section along Skyline Ridge and up the western face 

 of Frowning Ridge. The synclinal structure of these lava beds is 

 no less marked than that of the sedimentary beds of the Siestan. 

 Indeed, the two limbs of the syncline into which the lavas are 

 folded are perhaps the most prominent features of the Berkeley 



:; 'Proc. Cal. Acad. Sci., Ser. 2, Vol. IV, pp. 169. 170. 



