1914] Dickerson: Fauna of the Martinez Eocene of Calif ornia 103 



ribs instead of thirteen or fourteen. There is really no good evidence 

 to warrant placing this fauna in the Martinez. Until it has been 

 recognized with certainty at some other locality, or a better fauna has 

 been obtained at the original locality, its age will remain in doubt. 



SUMMARY OP MARTINEZ STRATIGRAPHY 



The greatest thickness of strata of Martinez age yet recognized in 

 California is exposed near the town of Lower Lake. These strata 

 probably represent the greatest length of time as well. The seven 

 hundred feet of strata beneath the first fossiliferous horizon, the 

 Meretrix dalli zone, are older than any strata known elsewhere in the 

 state, as the Meretrix dalli zone appears to represent a slightly earlier 

 period of Martinez time than this same zone at the base of the 

 Martinez in the area north of Mount Diablo. The Martinez at San 

 Pedro Point, San Mateo County, may be the equivalent of the Meretrix 

 dalli zone of the Lower Lake Martinez. The Troehocyathus zitteli and 

 Solen stantoni zones are not easily recognized at Lower Lake, but they 

 both appear to be present. 



The 2400 feet of strata at Benicia is probably the equivalent of the 

 upper 3300 feet of strata at Lower Lake. The Martinez of the type 

 locality is probably equivalent to the upper 2600-3000 feet of the 

 Lower Lake Martinez. The Martinez at Selby Smelter represents only 

 the middle portion of the Martinez, the Troehocyathus zitteli zone. 

 The Martinez north of Mount Diablo is equivalent to most of the 

 Meretrix dalli zone of the Lower Lake strata and to the Troehocyathus 

 zitteli zone of the type locality. The Solen stantoni zone appears to 

 be lacking in this section and is probably represented in the uncon- 

 formity between the overlying Tejon and the Martinez at this point. 

 The accompanying diagram presents the relations between the strata 

 of various localities graphically (see fig. 5). The sections given below 

 refer to their respective columns in figure 5. 



I. Section at Point San Pedeo, San Mateo County, California 



Feet 



( (5) Soft tan sandstone and shale 300 



Martinez! (4) Coarse-grained sandstone and conglomerate ) 



Eocene | (3) Fossiliferous beds | 300 



(2) Fine-grained sandstone, limestone and black shale 400 



400 



_ f (2) Fine-grained sandstone, limestone an 



Eocene(?)i ),( n 1 * a 1 



v 'I (1) Coarse sandstone and conglomerate 



Total 1400 



