INTRODUCTION AND ACKNOWLEDGMENTS. 



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



Errata. 



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



Page 112, 17th line, for " Jiucicolus'' ve&d fucicolus. 



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, 1 2th line from bottom, after Sowerby 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 ".7/. woodwardi" read N. woodwardi, and for " gibbsii" read 



gibbesii. 

 Page 243, 5th line, for " tenuispetm" read tenuispina. 

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

 Page 307, 17th and 19th lines, for " Calyptrea" read Calyplrma. 

 Page 339, 3rd line, for ' ' FissuridcB ' ' read Fissuridea. 



1. Leland Stanford Junior University: Geological Department collections. 



2. University of California: Geological Department collections, State Geo- 

 logical Survey collections, and State Mining Bureau collections. 



3. California Academy of Sciences: Paleontological and Conchological 



collections. 



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



California. 



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



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



(21 



, 9 ) September 22, 1802. 



