274 University of California Publications in Geology [Vol. 9 



first two of these are known to occur at upper Cretaceous localities 

 from British Columbia to the Santa Ana Mountains, California. 



Two mactrine species are now known from the Martinez Eocene 

 of this region. One, Mactra (?) tcnuissima Gabb, has been recognized 

 by Dickerson, 17 in material obtained from the Martinez group of 

 Lower Lake, Lake County, California. The other, Spisula (?) iveaveri 

 Packard, appears to be characteristic of the lower Eocene of Mount 

 Diablo and of the Santa Ana Mountains, California. The genera of 

 these forms have not been definitely determined, due to inability 

 to observe the hinges, and therefore they can have no place in a 

 phylogenetic discussion. 



Four species are known from the upper Eocene. Two, Spisula 

 merriami, n. sp., and S. tejonensis, n. sp., have a wide geographic 

 range, occurring abundantly at a number of Tejon localities through- 

 out the state, and S. tejonensis, n. sp., has been questionably 

 recognized by the writer from strata of approximately the same age 

 at Vader, Washington. The new species Spisula acutirostrata occurs 

 at the type locality of the Tejon group in California. The species 

 S. callistaeformis Dall, comes from the Stepovak series of Alaska. 



Spisida albaria ramonensis, n. var., and possibly S. occidentals 

 (Gabb) are restricted to the Agasoma gravidum zone, which according 

 to B. L. Clark is of Oligoeene age. 



Eleven species and one variety of well-known Mactrinae occur 

 within the Miocene strata of this region. This number is increased 

 by the following imperfectly known forms : Spisula lenticularis 

 (Gabb), S. montereyana (Arnold) and Mulinia landesi (Weaver). 

 Three and possibly four mactrine species are known in the Mon- 

 terey series, as now recognized, exposed in the vicinity of Mount 

 Diablo, California. S. catilliformis Conrad has been reported from 

 the Temblor of the Kern River district, Kern County, California, 

 associated with a fauna that is thought by B. L. Clark to be equiva- 

 lent to the Area montereyana zone of the Mount Diablo section. 

 S. selbyensis, n. sp., and a mulinoid form not distinctly separable 

 from Midinia densata Conrad also occur in this zone. Its variety, 

 M. densata var. minor occurs in the Turritella ocoyana zone of 

 the Coalinga district. The lower San Pablo mactrine fauna con- 

 sists of Spisida abscissa (Gabb), S. albaria (Conrad), S. catilliformis 



n Dickerson, R. E., Fauna of the Martinez Eocene of California, Univ. 

 Calif. Publ. Bull. Dept. Geol., vol. 8, p. 96, 1914. 



