140 University of California Publications in Geology [Vol. 13 



and Santa Margarita) . However, while this species has not definitely 

 been recognized from beds of Monterey age, specimens have been 

 found which indicate the possibility of this form extending into the 

 Monterey. Further collecting and better material may show that such 

 is the ease. 



In the San Pablo Bay region the Briones has been regarded as 

 consisting of three lithologic members. The faunal similarity of the 

 lower and upper sandstone members and the relatively non-persistent 

 character of the middle shale member, indicate that these three 

 members should be regarded as a single formation. 



The following fauna has been recognized from the lower sandstone 

 member of the Briones in the San Pablo Bay region : 



Area cf. trilineata Conrad Solen perrini Clark 



Chione panzana Anderson and Martin Solen cf. sicarius Gould 



Diplodonta harfordi Anderson Spisula albaria (Conrad) 



Diplodonta parilis (Conrad) Spisula catilliformis Conrad 



Diplodonta, sp. Spisula falcata brioniana, n. var. 



Dosinia cf. merriami Clark Tellina oregonensis Conrad 



Leda cf. taphria Dall Yoldia cooperi Gabb 



Maeoma andersoni Clark Calyptraea filosa (Gabb) 



Macoma cf. yoldiformis Carpenter Ficus rodeoensis English 



Marcia oregonensis (Conrad) Ficus stanfordensis Arnold 



Modiolus cf. capax Conrad Fusinus, sp. 



Mya ovalis (Conrad) Koilopleura sinuata (Gabb) 



Panope cf. generosa Gould Nassa whitneyi, n. sp. 



Pecten andersoni gonicostus, n. var. Natica kirkensis Clark 



Pecten raymondi brionianus, n. var. Natica pabloensis Clark 



Phaeoides annulatus (Eeeve) Siphonalia rodeoensis, n. sp. 



Sehizothaerus nuttallii (Conrad) Thais cf. lima (Martyn) 



Siliqua lueida (Conrad) Turris, sp. 



All these forms except the following have been found in the Briones 

 formation in other localities : 



Diplodonta, sp. Ficus rodeoensis English 



Leda cf. taphria Dall Fusinus, sp. 



Macoma andersoni Clark Thais cf. lima (Martyn) 



Pecten andersoni gonicostus, n. var. Turris, sp. 



Of these eight species, five are not accurately determinable, and 

 one, Macoma andersoni Clark, is found in the San Pablo above. Only 

 two determinable species are restricted to this lower sandstone, and 

 only one specimen of each of these two species has so far been found. 



All the species found in this lower sandstone which also occur in 

 the Monterey group, have been found in the Briones formation in 

 other regions. 



