FORAMINIFERA FROM THE TERTIARY OF 



CALIFORNIA. 



BY FREDERICK CHAPMAN, 



Assoc. Linn. Soc. Lond. 



Plates XXIX, XXX. 

 Introduction. 



In consideration of the value of Foraminifera as indices 

 of the relative age of a fossiliferous deposit, not so much 

 with regard to isolated species, but with the general faunal 

 aspect of the group, the present collection affords many 

 points of interest. 



Presuming the conditions of life and surroundings to be 

 equal, we may fairly expect to find foraminiferal assem- 

 blages in many different areas of the earth's superficial 

 deposits very closely related as to their percentage of spe- 

 cies in common, provided they are comparable with one 

 another, either homotaxially (with regard to higher groups 

 of animal remains), or chronologically. On the other hand, 

 we rarely find foraminiferal assemblages from deposits of 

 decidedly different ages with a high percentage of species 

 in common. 



In March, 1897, I was favored by Dr. J. C. Merriam of 

 the University of California with a sample of Tertiary marl 

 from California, accompanied by a request that I would 

 investigate the rock for its Foraminifera. 



In November of the same year Dr. Merriam supplied me 

 with further specimens of a somewhat similar rock, and 

 which was richer in organisms than that first sent. 



All the samples have now been examined and yield the 

 following results. 



The sample first received, labeled " Miocene (?) Cali- 

 fornia," is a close-textured grey-brown marl. The frac- 

 tured surface of the rock when examined with a lens 

 reveals numerous foraminiferal shells, broken across, and 

 with the chambers quite empty. This sample did not afford 



[241] December 21, 1900. 



