74 University of California Publications in Geology [VOL. 8 



FAUNA OF THE MERETRIX DALLI ZONE IN THE MARTINEZ NORTH OF MOUNT DIABLO 



(Continued) 



Of the forms in the above list the following as far as known are 

 characteristic of this lower zone : Cidaris, sp., Terebratulina tejonensis 

 Stanton, Cardita veneriformis Gabb, Gorbula, sp., Leda milleri, n. sp., 

 Meretrix stantoni, n. sp., Meretrix dalli, n. sp., Spisula(f) weaver i 

 Packard, Zirphaea(f), sp. and Tritonium martinezemis, n. sp. Schiz- 

 aster lecontei Merriam is very rare in these beds, only one specimen 

 being found. The striking thing, however, is the absence of such 

 forms as Trochocyathus zitteli (Merriam), Modiolus merriami Weaver, 

 Crassatellites grandis Gabb, Anchura gabbi, n. sp., Ficopsis, sp., 

 Neptunea cretacea Gabb, and Surcula fairbanksi, n. sp. 



The large number of pelecypods in comparison to the gastropods 

 is very noteworthy. The coarse character of the sediments indicates 

 that they were deposited in shallow water and in part even within the 

 littoral zone, as the presence of Zirphaea(f), sp., proves. How much 

 this depth factor was influential in giving distinctiveness to this fauna 

 will be discussed after the middle or Trochocyathus zitteli zone has 

 been considered. 



FAUNA OF THE TROCHOCYATHUS ZITTELI ZONE 

 Three to four hundred feet above the base of the Martinez, another 

 very distinct zone is found in hard, gray-green, glauconitic sandstone. 

 This zone is characterized by Trochocyathus zitteli (Merriam). Its 

 fauna is tabulated below. 



