86 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



but it Stretches close under and half a mile beyond 

 Point Dume, only 400 yards from the low cliffs, and forms 

 the head of the submerged valley that runs out to the SE. 

 by S., and drops off to 238 fathoms in 15^ miles (1,428 

 in 6,600 feet), and less than a mile from Dume. The dis- 

 tance between the 225 fathom curves at the deepest part is 

 less than half a mile. Unfortunately there are no soundings 

 beyond this. In fact there are so few soundings that 

 the characteristics of the bottom have not been given; but 

 on both sides we find gray sand at 25 fathoms, and green 

 mud at 125 fathoms. 



The geographical position of the head of the valley is : 

 Latitude 35°, 00' N.; longitude 118°, 49' W. 



8. The Point Mugu Submerged Valley. 



This submerged valley lies at the eastern side of the Santa 

 Clara Valley, near the eastern entrance to the Santa Barbara 

 Channel. Fourteen miles west, northwest from Point Dume, 

 the mountain mass of Santa Monica terminates abruptly, 

 dropping from 1,427 feet to the Laguna Mugu in less than a 

 mile. Then the shore takes an outward, slightly convex 

 curve for 15 or 16 miles, to San Buenaventura, with a 

 low sand-shore immediately backed by an indurated sand 

 that towards the west reaches 65 feet high as a steep cliff. 

 This broad, flat, and slightly rising plain of the Santa Clara 

 stretches many miles inland between high mountains, and 

 through the western part of the valley runs the Santa Clara 

 River. Where the plain meets the eastern mountain is the 

 Laguna Mugu, with extensive marshes and a low, narrow 

 sand beach, with a slight tidal opening as if the river may 

 at one time have emptied here. Close upon this sand beach 

 heads a double-armed, submerged valley, of which the 

 details are readily given from the numerous soundings out 

 to 500 fathoms. 



The main axis of the Point Mugu Valley comes from 

 about 475 fathoms at 11 miles SE. by S. from the head and 



