t Clark: The San Lorenzo Series of Middle California 121 



ACILA MUTA MARKLEYENSIS, n. var. 



Plate 13, figure 3 |i;f1. 

 Type specimen 11195, Coll. Invert. Palae. Univ. Calif., loc. 1131 

 This variety is distinguished from the typical A. muta in that 

 the height is greater in proportion to the length; this character can 

 readily be seen by comparing the figures of the two forms. The 

 variety is found at locality 1131, about a half-mile to the south of 

 the town of Walnut Creek ; here it is associated with the typical form 

 of the species. It occurs in great abundance at locality 3081, on the 

 west side of Markley Canon, in the section north of Mount Diablo; 

 here all the forms found were of the high type, the typical form 

 apparently being absent. 



ACILA SHUMARDI Dall 



Plate 13, figures 7, 8 and 17 



Nucula (Aoila) decisa Dall, not Acila decisa Conrad. Trans. Wagner Free 

 Inst. Sei., vol. 3, pt. 4, p. 573, 1895; figured in vol. 3, pt. 5, pi. 40, figs. 

 1, 3, 1900. 



Nucula (Acila) shumar&i Dall, U. S. Geol. Surv., Prof, paper no. 59, 

 p. 103, 1904. 



Nucula dalli Weaver, not Arnold, Wash. Geol. Surv., Bull. 15, p. 18, 1912. 

 No adequate description has ever been given of this species. It 

 was first listed by W. H. Dall as Nucula {Acila) decisa Conrad ; later 

 it was given a new name. 00 Dall at first thought that Acila decisa 

 Conrad was the same as A. divaricata; afterwards, however, he gave 

 the name A. conradi Dall to a form found in the Empire beds (Upper 

 Miocene) near Coos Bay, Oregon, considering this to be synonymous 

 with Conrad's species, A. divaricata; at the same time he expressed 

 the opinion that A. decisa Conrad was indeterminate and for this 

 reason he gave to the shell formerly figured as that species the name 

 A. shumardi. The specimen figured, which must be considered as the 

 type, came from near the old town of Pittsburg, Oregon. The beds 

 in which it was found were originally determined to be Eocene in age. 

 The writer, 91 in his paper, "The occurrence of Oligocene in the Contra 

 Costa Hills of Middle California," listed all the species known by 

 him at that time from the Pittsburg locality, the conclusion being 

 that this fauna is Oligocene rather than Eocene, and is very closely 

 related to the Agasoma gravidum fauna of Contra Costa County. 

 California. One of the specimens figured in this paper comes from 



so U. S. Geol. Surv., Prof, paper no. 59, pp. 102-103, 1909. 



si Clark, B. L., Univ. Calif. Publ., Bull. Dept. Geol., vol. 9, no. 2, p. 18, 1915. 



