Clark: The San Lorenzo Series of Middle California 95 



The following species are common to the Kirker formation to the 



north of Mount Diablo and to the Kirker tuffs and Concord formation 



of the Sobrante anticline : 



Acila gettysburgensis Reagan Solen gravidus, n. sp. 



Acila shumardi Dall Spisula ramoncnsis Packard 



Malletia packardi, n. sp. Tellina lorenzoensis Arnold 



Modiolus pittsburgensis, n. sp. Agasoma gravidum Gabb 



Phaeoides cf. aeutilineatus Con- Pseudoperissolax merriami, n. sp. 



rad Solarium lorenzanum Arnold 



The opinion has already been expressed that beds representing the 

 Kirker formation are not present in the section at Walnut Creek. 

 Whether there was a land area in this vicinity during the deposition 

 of the Kirker beds at the Sobrante anticline and to the north of the 

 mountain, or whether erosion has removed them after deposition, can- 

 not be determined with the data at hand. 



It would seem that the shoreline at the time of the deposition of 

 the San Lorenzo beds of this region, or at least during part of the 

 period, was in the vicinity of Mount Diablo and that there were 

 oscillations of the ocean level, as indicated by the disconformities 

 which have been described and by the alternation of fairly deep-water 

 with shallow-water deposits. This is only additional evidence that 

 the earth's crust in the vicinity of Mount Diablo was a positive 

 element during Mesozoic and Cenozoic time, the shorelines of the 

 various seas during the different epochs of deposition being most of 

 the time in the near vicinity. Shallow-water deposits of considerable 

 thickness of Cretaceous, Eocene, Oligocene, and Miocene age are 

 found in this section. 



Complete List of Species from San Lorenzo Series in Eegion of 

 Mount Diablo 



A — Species common to Pittsburg beds, Oregon. 



B — Species common to Lincoln and Porter Creek beds, Washington. These 

 localities belong to what is usually considered Lower Oligocene. 



C — Species common to beds in Oregon, Washington and Vancouver Island, 

 containing the Acila gettysburgensis fauna. 



D — Species common to the Lower Miocene, i.e., Turritella inezana and Tur- 



ritella ocoyana zones. 



Pelecypoda A B C D 



Acila gettysburgensis Reagan x 



Acila mutaj n. sp x 



Acila muta markleyensis, n. var 



Acila shumardi Dall x x 



Antigona (Artena) mathewsonii (Gabb) x 



Antigona (Artena) negleeta, n. sp 



