474 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



Material Examined : 



Locality 



Collector 



Where Deposited 



Formation 



Period 



Chiton Bed, Pt. Fermin, Cal. 

 Chiton Bed, Pt. Fermin, Cal . 

 Chiton Bed, Pt, Fermin, Cal . 



Near lighthouse, Pt. Fermin, 

 Cal 



Near lighthouse, Pt. Fermin \ 

 Cal / 



Nob Hill Cut, San Pedro, Cal. 



Crawfish George's, San Pedro, 



Cal 



Crawfish George's, San Pedro, 



Cal 



? Deadman Id., San Pedro, 



Cal 



? Deadman Id., San Pedro, 



Cal 



Deadman Id., San Pedro, Cal. 



Deadman Id., San Pedro, Ca!. 



Deadman Id., San Pedro, Cal. 



Deadman Id., San Pedro, Cal. 



Deadman Id., San Pedro, Cal. 



E. P. Chace, 1918 



E. P. & E. M. Chace, 1918 



E. P. Chace & S. S. Berry, 



1920 



E. P. & E. M. Chace, 1918 



E. P. & E. M. Chace, 1918 

 OldroydColl 



E. P. & E. M. Chace, 1918 



E. P. & E. M. Chace, 1918 



OldroydColl 



OldroydColl 



Arnold Coll 



Arnold Coll 



Arnold Coll 



Arnold Coll 



Arnold Coll 



Berry Coll. Cat. 4043 . 

 Chace Coll 



Chace Coll 



Berry Coll. Cat. 4112. 

 (Berry Coll. Cat. 4112 



\Cal. Acd. Sci 



Dept. Geology, 

 Stanford Univ 



Berry Coll. Cat. 4047. 



Berry Coll. Cat. 4047. 

 Dept. Geology, 

 Stanford Univ 



Berry Coll. Cat. 5184. 

 Dept. Geology, 



Stanford Univ 



Dept Geology, 



Stanford Univ 



Dept. Geology, 



Stanford Univ 



Dept. Geology, 



Stanford Univ 



Dept. Geology, 



Stanford Univ 



[ 949] 

 [1029] 



[1415] 



[1105] 



[1106] 



[651] 

 [ 955] 

 [ 956] 

 [ 669] 

 [648] 

 [ 708] 

 [ 722] 

 [ 723] 

 [ 724] 

 [ 730] 



Lower San Pedro. . 

 Lower San Pedro . . 



Lower San Pedro . 



Lower San Pedro. . 



Lower San Pedro. . 



Lower San Pedro. . . 

 Lower San Pedro. . 

 Lower San Pedro. . 

 ? "Upper San Pedro' 

 ?"Upper San Pedro' 



? 



? 



? 



? 



? 



Pleistocene 

 Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



Pleistocene 



? Pleistocene 



? Pleistocene 



? Pleistocene 



? Pleistocene 



? Pleistocene 



Remarks: This common central and northern California 

 species appears to be of rather frequent occurrence in the Plei- 

 stocene around San Pedro, being probably characteristic of the 

 Lower San Pedro Series. Whereas in the recent state it is 

 much less common as a rule than its associate, /. mertensii, the 

 reverse is true of the fossils. 



/. mertensii is the only species with which it is likely to be 

 confounded. In the case of valves ii-vii, however, even very 

 fragmentary specimens are readily identifiable by the extremely 

 numerous, crowded, transverse bars connecting the longitudinal 

 riblets of the central areas, making their interspaces appear 

 finely, but distinctly striate to the unaided eye. The lines of 

 growth give a similar, but coarser effect of striation to the 

 interspaces between the lines of more or less coalescent pustules 

 on the head valve, so that this too has a certain individuality 

 of aspect very helpful in distinguishing it from the correspond- 

 ing valve in mertensii. 



