INTRODUCTION AND ACKNOWLEDGIMENTS. 



The field work upon which this paper is based began in the winter of 1886, 

 when the writer first visited the fossil-bearing beds of San Pedro. Since that time 

 several visits have been made each year to the beds in that vicinity, generally after 

 heavy rains, when landslides and the breaking ofif of the banks have given new 



ii- - 11. 



Errata. 



Page 107, last line, after (Cooper) insert San Pedro; Santa Barbara (Arnold). 



Page 112, 17th line, for "JJuricohis'' read /ucuoliis. 



Page 142, last line, after Cytherea insert radiata Sby. 



Page 144, 4th line from bottom, after Carpenter insert var. 



Page 145, 4th line, for "C. diaphana" read C. subdiaphana. 



Page 166, i2th line from bottom, after Soiverby insert var. 



Page 185, top line of foot-note, for " Dr. W. N. Dall" read Dr. W. H. Dall. 



Page 233, nth line from bottom, for "J/, woodwardr read N. u-oodwardi, and for " pMsH" read 

 gibbesii. 



Page 243, 5th line, for " fenuispena" read temiispina. 



Page 253, 7th line, for " stuarti Smiih var." read orpheus var. 



Page 307, 17th and 19th lines, for " Cafyptrea'' read Calyptr^a. 



Page 339, 3rd line, for '' Fissurida" read Fissuridea. 



3. California Academy of Sciences: Paleontologicul and Conchological 

 collections. 



4. The private collection of Mrs. M. Burton WilIiam.son, Los Angeles, 

 California. 



5. The private collection of Mrs. T. S. Oldroyd, Los Angeles, California. 

 (). The private collection of Mr. Henry Hemphill, San Diego, California. 



( i ) ( 9 J September 22, 1902. 



