570 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



which prevails in this region today, an interglacial epoch. 

 The Tomales formation is largely land or stream-laid de- 

 posits. During a portion of Tomales-Pleistocene time, how- 

 ever, the region was occupied by a shallow bay. Both its 

 fauna and flora testify conclusively a milder climate for the 

 Tomales epoch. 



Undifferentiated Pleistocene 



It has been indicated incidentally in the description of the 

 Merced group that marine and stream terraces occur both in 

 the Point Reyes Triangle and the uplifted mainland block. 

 Unfortunately, but little fossil material has been obtained 

 from these terraces of the Point Reyes Triangle. The general 

 profile of the western face indicates unmistakably that the sea 

 was the agent which cut these gigantic steps. Likewise, the 

 even surface which truncates the Merced around Freestone 

 is so broad and level that any other erosion agency except the 

 sea could not have done this planing. Osmont reports some 

 boring mollusks in and around Occidental but the writer was 

 unable to find the locality. 



Pleistocene stream gravels were noticed in the Petaluma 

 Quadrangle, three-quarters of a mile southwest of Waugh 

 School, in a road-cut. At this locality a very evident ero- 

 sional unconformity is present between the Pleistocene gravels 

 and the underlying yellow tuffaceous sandstone of the Merced. 



Another interesting stream channel is found in the State 

 Highway a quarter of a mile northwest of Penn Grove. This 

 old stream channel is full of gravel in which large fragments 

 of petrified wood are found. The direction in which the 

 stream flowed in Pleistocene time is apparently at right angles 

 to the drainage of the present day. A similar suggestion of 

 an east-west drainage during upper Pleistocene time was ob- 

 tained from a study of the stream gravels at Waugh School. 

 From other evidence it appears probable that during a portion 

 of Pleistocene time the streams of this vicinity did actually 

 drain into the streams entering Tomales Bay. 



Dr. Chester Stock found interesting mammalian remains 

 in Pleistocene beds one-half mile northwest of the Iowa 

 School. This locality is in the Santa Rosa Quadrangle near 



