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University of California Publications in Geology [Vol.9 



the fossiliferous horizons the beds have been much indurated, causing 

 these strata to outcrop prominently. Of minor importance are shale, 

 rhyolitic tuff, and thin layers of coal. A bed of silicious limestone 

 having a thickness of about ten feet was traced more than one-half mile 

 until cut off by faulting. A short distance above and below the lime- 

 stone marine fossils were found. The beds of coal, the coarseness of 

 the sandstones and conglomerates, the variation of the lithology within 

 short distances, and the character of the mulluscan fauna may be 

 taken as indicative of deposition under shallow water conditions. The 

 occurrence of quantities of gypsum at some localities, if it can be 

 proved to be interstratified with the clastic rocks, may indicate that 

 in part the beds are terrestrial or that the basin of deposition was 

 nearly isolated from the sea. 



Fauna of the Lower Pliocene on Jacalitos Creek and 



In the lower 800 to 1500 feet of the Jacalitos fossils are rare 

 and where they appear the state of preservation is such that no 

 diagnostic fauna has been obtained. In the upper horizons at some 

 localities fossils occur in abundance. In most instances, however, the 

 character of the material is not ideal for the preservation of the smaller 

 forms, or the mulluscan shells have been crushed or leached out. In 

 some parts of the area numerous faults limit the tracing of fossil 

 horizons except for short distances. At a few localities the prominent 

 indurated beds can be followed, otherwise the striking bands of white 

 tuff, where present, are the best horizon markers. 



The following list comprises the fauna obtained in the beds that 

 have been mapped as Jacalitos at the type locality and the beds of 

 corresponding age on Waltham Creek. 



Waltham Creek 



ECHINODERMATA 



Astrodapsis jacalitosensis Arnold 

 Astrodapsis peltoides Anderson and Martin 

 Echinarachnius gibbsii (Eemond) 



Pelecypoda 



Area trilineata Conrad 

 Cardium quadrigenarium Conrad 

 Chione elsmerensis English 

 Chione, cf. fernandoensis English 



Cryptomya californiea (Conrad) 

 Cryptomya quadrata Arnold 

 Cumingia, cf. californiea Conrad 

 Cyrena californiea Gabb 



