EXPLANATION OF PLATE 4 



Fig. la. Strongylocentrotus franoiscanus A. Agassiz. Specimen 11389, Univ. 

 Calif. Coll. Invert. Pal. Upper surface of test. X 1V2- Ventura County, Calif. 

 Upper Fernando formation, Upper Pliocene. 



Fig. lb. Strongylocentrotus franciscanus A. Agassiz. Same specimen. Lower 

 surface of test. X 1%. 



Fig. \c. Strongylocentrotus franciscanus A. Agassiz. Same specimen. Lateral 

 surface of test. X 1%. 



Fig. 2a. Sismondia{?) arnoldi Twitchell. Holotype specimen 165538, U. S. 

 Nat. Mus. Upper surface of test. X 2. Coalinga district, Fresno County, Calif. 

 Etcliegoin formation, Lower Pliocene. 



Fig. 26. Sismondia{?) arnoldi Twitchell. Same specimen. Lower surface 

 of test. X 2. 



Fig. 3o. Sismondin {?) coalingaensis Twitchell. Holotype, specimen 165717, 

 U. S. Nat. Mus. Upper surface of test. X 2. Coalinga district, Fresno County, 

 Calif. Etehegoin formation. Lower Pliocene. 



Fig. 3b. Sisinondia{?) coalingaensis Twitchell. Same specimen. Lower sur- 

 face of test. X 2. 



[160] 



