Vol. 6] 



Dickerson: Martinez Formation. 



177 



Leda gabbi. Turrit ell a pachecoensis, Flabellum remondianum, 

 Galerus excentricus, Cylichna costata, and Dentalium cooperi. 

 The first nine are characteristic of the Martinez, while the rest 

 are also found in the Tejon. The last two are the only ones 

 occurring in the Chieo as well as in the Martinez and the Tejon. 



For a half-mile the contact between the Chieo and Martinez 

 at the locality south of Stewartville is denned by abundant and 

 clearly marked borings of Zirphaea (?). These borings are in 

 Chieo sandstone and limestone, but they are filled with material 

 entirely different from the rock which is penetrated by them. 

 There seems to be no question that the borings mark the shore 

 line of the Martinez sea as it encroached upon a land surface 

 formed of elevated and eroded Chieo rock's. 



Tra nsm itted February 1, 1911. 



