200 University of California Publications in Geology [Vol. 9 



correlated with the Etchegoin formation north of Coalinga, while the 

 lower part was given the formational name Jaealitos. This division 

 was based chiefly on palaeontologic evidence, as the two formations 

 wherever found in contact are apparently conformable. The fauna 

 obtained from the Jaealitos was, however, small and the greater 

 number of the species listed either new or of very long range. As a 

 consequence the Jaealitos has been grouped with the underlying Santa 

 Margarita formation by some California palaeontologists and geologists 

 and with the overlying Etchegoin by others. 



In the present paper a fauna of 82 species is listed. Although a 

 number of the species have a long range and a few are new, yet the 

 fauna seems large enough to fix the position of the beds of this lower 

 horizon on Jaealitos Creek and Waltham Creek more definitely in the 

 stratigraphic column than has been possible heretofore. 



Historical Review 



The Neocene in this region was first described in a publication by 

 P. M. Anderson, 1 who considered what has later been mapped as 

 Jaealitos and Etchegoin equivalent for the most part to the several' 

 lithological units grouped in what were called the Coalinga Beds, north 

 of the town of Coalinga. In a later paper the same author 2 restricted 

 his definition of the Coalinga Beds "to the lower portion of a series 

 which is unconf ormably related to the older members of the Miocene. ' ' 

 At what locality this occurs or to what unconformity this has reference 

 is not known to the writer. 



A report by Ralph Arnold 3 on the palaeontology of the district 

 contains a brief description of the geology and advances evidence for 

 the separation of the Jaealitos from the adjoining formations. 



In a bulletin dealing with the geology and oil resources of the 

 Coalinga district by Ralph Arnold and Robert Anderson 4 the Jaealitos 

 was described as being separable, at least faunally, from the Santa 

 Margarita and Etchegoin formations. In this publication overlap 

 was also used as evidence for the separation of the Jaealitos from the 

 Etchegoin. The section on Jaealitos Creek was taken as the type 

 section of the formation of that name, this being a part of the area 

 covered by the present paper. 



1 Anderson, F. M., A Stratigraphic Study in the Mount Diablo Kange of 

 California, Proc. Calif. Acad. Sci., 3d ser., vol. 2, no. 1, 1905. 



2 Anderson, F. M., A Further Study in the Mount Diablo Kange of California, 

 Proc. Calif. Acad. Sci.. 4th ser., vol. 3, 1908. 



3TJ. S. Geol. Surv., Bull. 396, 1909. 

 *TJ. S. Geol. Surv., Bull. 398, 1910. 



