106 University of California Publications in Geology [Vol. ll 



Since the appearance of Merriam's paper, the Agasoma gravidum 

 fauna of Contra Costa County has generally been correlated with 

 that of the Turritella oeoyana zone. In 1905 F. M. Anderson, 77 in 

 his paper, "A stratigraphic study of the Mount Diablo Range of Cali- 

 fornia," accepted the fauna of the Agasoma gravidum zone, as listed 

 by Merriam, as being of the same age as the fauna from his Temblor. 

 Ralph Arnold, 78 in his paper "The Tertiary and Quartenary Pectens 

 of California," listed the Agasoma gravidum fauna with that of the 

 "Vaqueros sandstone" (Lower Miocene). In this list the Turritella 

 inezana fauna and the Turritella oeoyana fauna are both included. 

 Professor J. P. Smith, 70 in a correlation table of the Neocene section 

 of California in a paper entitled ' ' The geologic record of California, ' ' 

 includes the Agasoma gravidum fauna of Contra Costa County in the 

 Turritella oeoyana zone, listing the latter species as having been found 

 in Contra Costa County. In 1912, Smith, 80 in his paper, "The geo- 

 logic range of Miocene invertebrate fossils of California," again 

 included the Agasoma gravidum fauna with that of the "Temblor," 

 using this name as equivalent to the Turritella ocoj^ana zone. How- 

 ever, both faunas, "Vaqueros" and "Temblor," are considered by 

 him to belong to the same general period of deposition. In this con- 

 nection he makes the following statement : 



Instead of the numerous subdivisions recognized by most stratigraphers, there 

 are, in fact, only two major faunal units in the Miocene of California; a lower, 

 including all the faunas up through the Monterey, and an upper, including the 

 San Pablo, Santa Margarita, and Etehegoin faunas. The division line between 

 them corresponds to the period of orogenic activity that came at the end of the 

 Monterey epoch. si 



At another place in the paper, we find the following statement : 



This lowest horizon of the Miocene has been called by Merriam the zone of 

 the Turritella hoffmani (Turritella inezana) ; it may eventually be found to be 

 an inshore equivalent of the deep-water San Lorenzo Oligocene, with which it has 

 a few species in common. s - 



G. D. Louderback, 83 in his paper "The Monterey series of California," 

 contends that the formations generally classed as Lower Miocene 



« Anderson, F. M., Proc. Calif. Acad. Sci., ser. 3, Geo!., vol. 2, no. 2, p. 186, 

 1905. 



-s Arnold, Ralph, U. S. Geol. Surv., Prof. Paper no. 47, p. 19, 1906. 

 "9 Smith, J. P., Jour. Geol., vol. 18, no. 3, see face plate opposite page 226, 

 1912. 



so Smith, J. P., Proc. Calif. Acad. Sci., ser. 4, Geol., vol. 3, pp. 161-182, 1912. 

 si Op. tit., p. 162. 

 Ibid., p. 165. 



83 Louderback, G. P., Univ. Calif. Publ., Bull. Dept. Geol., vol. 7, no. 10, pp. 

 177-241, 1913. 



