348 CALIFORNIA ACADEMY OF SCIENCES. 



southward the sea has cut a fine section of these beds. 

 The deposits here are at least 150-200 feet thick. At the 

 bottom is a heavy bed of sand having the pecuhar struc- 

 ture of sanddunes. This rests upon the surface of the 

 old eruptive rock which makes up Mussel Rock. Above 

 the geolian deposit are marine deposits of sand and gravel 

 to the top of the terrace, the gravel being largely frag- 

 ments of the old igneous rock. See plate xxv. 



In the ravine a short distance south of Mussel Rock, 

 the deposit is a difficult one to understand. Between the 

 wind deposit and igneous rock are several argillaceous 

 sandy layers which are not strictly conformable among 

 themselves, but appear to have been laid down during a 

 comparatively rapid rising of the shore. Over these beds 

 come the wind deposits, and above those the marine de- 

 posits of sand and gravel. A short distance south the 

 sand loses its gravel, and, except at a few places where 

 the irregular surface of the igneous rock is exposed above 

 the beach, the deposit continues to be sand to the end of 

 the section at sea level. Near each exposure of igneous 

 rock, the deposit is largely made up of fragments of the 

 rock. 



On the north side of Mussel Rock, just above the ig- 

 neous rock, fragments of wood and cones of a conifer 

 are found. Dr. Lawson reports these on the authority of 

 Professor E. L. Greene to be Pinus insignis, or Monterey 

 pine. Dr. Lawson,* however, placed the beds contain- 

 ing these cones below the Merced series. My observa- 

 tions make them a part of the nearly level strata lying on 

 the surface of the ip;neous rock from which the Merced 

 series had been eroded. These are the same as the 

 nearly level strata better exposed on the south of Mussel 

 Rock. 



^ Univ. of Cal., Bull. Dept. Geol., vol. i, p. 143. 



