146 University of California Publications in Geology [Vol. 13 



formation should be included in the San Pablo group rather than in 

 the Monterey, or in a distinct group of its own. 



That the Briones is a distinct formation from the Lower San 

 Pablo (Cierbo) has already been shown by Merriam 14 on the basis 

 of the sea-urchins. The Briones form, Astrodapsis brewerianus 

 (Remond) has not been found in the Lower San Pablo, and the Lower 

 San Pablo form, Scutella gabbi (Remond) has not been observed in 

 the Briones. 



The Briones has twenty-one species that have not been found in 

 other formations ; the Lower San Pablo has twenty-one species that are 

 peculiar to it ; and there are only five species which are restricted to 

 these two formations. This indicates a faunal distinctness. 



The following are the twenty-one species peculiar to the Briones : 



Astrodapsis brewerianus (Bemond) 

 Astrodapsis brewerianus diablo- 



ensis Kew 

 Antigona willisi, n. sp. 

 Leda furlongi, n. sp. 

 Modiolus gabbi subconvexus n. var. 

 Modiolus veronensis, n. sp. 

 Peeten andersoni gonieostus, n. var. 

 Peeten ricei, n. sp. 

 Peeten tolmani Hall and Ambrose 

 Peeten vickeryi, n. sp. 



Spisula falcata brioniana, n. var. 

 Tivela merriami, n. sp. 

 Venus brioniana, n. sp. 

 Calliostoma obliquistriata, n. sp. 

 Fieus rodeoensis English 

 Koilopleura sinuata (Gabb) 

 Nassa whitneyi, n. sp. 

 Oliva simondsi, n. sp. 

 Sinum trigenarium, n. sp. 

 Siphonalia rodeoensis, n. sp. 

 Trophon daviesi, n. sp. 



The following are the twenty-one species peculiar to the Lower San 

 Pablo 1 5 (Cierbo) : 



Calyptraea diabloensis Clark 

 Cerithiopsis turneri Clark 

 Chrysodomus eierboensis Clark 

 Chrysodomus pabloensis Clark 

 Columbella pittsburgensis Clark 

 ITemifusus dalli Clark 

 Littorina remondii Gabb 

 Murex (Oeinebra) selbyensis Clark 

 Thais eierboensis Clark 

 Trophon dickersoni Clark 



Asterias remondii Gabb 

 Scutella pabloensis Kew 

 Peeten eierboensis Clark 

 Peeten crassiradiatus Clark 

 Peeten weaveri Clark 

 Pitaria behri Clark 

 Pitaria stalderi Clark 

 Sanguinolaria alata (Gabb) 

 Spisula abscissa (Gabb) 

 Tivela diabloensis angulatum Clark 

 Bursa carinata Clark 



The following are the five species peculiar to the Briones and the 

 Lower San Pablo : 



Dosinia merriami Clark 

 Ostrea bourgeoisi Bemond 

 Tivela diabloensis Clark 



Trophon gracilis elarki, n. nom. 

 Natica kirkensis Clark 



i* Merriam, J. C, Distribution of the Neocene sea-urchins of Middle Cali- 

 fornia, Univ. Calif. Publ. Bull. Dept. Geol., vol. 2, p. 117, 1898. 



is Clark, B. L., Fauna of the San Pablo group of Middle California, Univ. 

 Calif. Publ. Bull. Dept. Geol., vol. 8, pp. 417-423, 1915. 



