74 University of California Publications in Geology [Vol. 8 



Fauna op the Meretrix dalli Zone in the Martinez North op Mount Diablo 



(Continued) 



Loc. Loc. Loc. Loc. 



1745 1556 1743 1557 



Fusus, sp ! x 



Galerus excentricus Gabb .... .... x 



Heteroterma striata Stanton x 



Lunatia hornii Gabb x 



Natica, sp., a x 



Natica (Gyrodes) lineata, n. sp x x 



Neptunea mueronata Gabb x x 



Perissolax triearnatus Weaver x 



Ringinella pinguis Gabb .... x 



Surcula merriami, n. sp .... x 



Tritonium martinezensis, n. sp x x x 



Turritella infragranulata Gabb x x x 



Turritella paehecoensis Stanton x 



Urosyca caudata Gabb x .... x 



Xenophora zitteli Weaver x 



Fish tootli .... x 



Leaf .... x 



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 venerif ormis Gabb, Corbula, sp., Leda milleri, n. sp., 

 Meretrix stantoni, n. sp., Meretrix dalli, n. sp., Spisula(f) weaveri 

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

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

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

 forms as Trocliocyathus 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 e 

 littoral zone, as the presence of Zirpli,aea( ?), sp., proves. How much 

 this depth factor was influential in giving distinctiveness to this fauna 

 will be discussed after the middle or Trocliocyathus 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 Trocliocyathus zitteli (Merriam). Its 

 f u una is tabulated below. 



