II. 



FOSSIL FISHES OF THE (MIOCENE) MONTEREY 

 FORMATIONS OF SOUTHERN CALIFORNIA 



DAVID STARR JORDAN and JAMES ZACCHEUS GILBERT. 



Southern California, as the term is used in this paper, includes all 

 that -part of the state lying to the southward of the arbitrary straight 

 line which forms the northern boundary of the counties of San Luis 

 Obispo and Kern. Much of the surface rock of this region belongs to 

 the Miocene age. This is especially true of large sections of the counties 

 of Los Angeles, Santa Barbara, and Kern. 



The most notable feature of the Miocene deposits lies in the fact 

 that in places hundreds of feet are composed solidly of diatoms, forming 

 a very white shaly rock of low specific gravity and extremely friable. 

 This is known as Celite, and the organic matter it once contained is 

 thought to be a source of the oil which abounds in the same general 

 region. 



In certain places these rocks, in the so-called Puente formation of 

 the Monterey period, abound in remains of fossil fishes. These are mostly 

 of small size and delicate structure, inhabitants of shallow bays, and while 

 most of them represent extinct genera, the general character of the fish- 

 fauna does not differ widely from that of the California fauna of today. 



The present writers will not venture on a discussion of the stratig- 

 raphy of this region, nor on the conditions under which such prodigious 

 masses of diatoms were deposited. It would appear that the region 

 south of the Tehachapi range was composed of sheltered islands in, an 

 arid region, the temperature not far from that of San Diego today. The 

 diatoms may have been driven from the open ocean by the trade winds. 

 The region must have been arid, else sand would have been washed in 

 and mixed with the diatom deposits. In some districts this is the case. 



The small size of the fishes and the fact that all or most of them 

 are shore species would indicate bays of small extent or an archipelago 

 of small islands. Sharks' teeth are common in rocks of this period else- 

 where, but none have been found in the diatomaceous shales. These 

 shales have been sometimes segregated as the Puente formation, a matter 

 which we must leave to geologists. 



As to the nature of the deposits called Monterey or Puente, we have 

 the following information from Dr. Frank M. Anderson: 



