EXPLANATION OF PLATE 20 



Figures approximately natural size. 



Fig. la. Astrodapsis jacalitosensis Arnold. Holotype, specimen 165610, U. S. 

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

 Etchegoin (Jacalitos) formation, Lower Pliocene. Photographed by U. S. Geo- 

 logical Survey. 



Fig. lb. Astrodapsis jacalitosensis Arnold. Specimen 11037, Univ. Calif. 

 Coll. Invert. Pal. Lower surface of test. Coalinga district, Fresno County, Calif., 

 Univ. Calif, loc. 2688. 



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