280 



University of California Publications. 



\ Geology 



Test oval to sub-circular in outline, longitudinal axis slightly 

 longer than transverse one ; depressed, abactinal surface gently 

 arched, actinal surface slightly concave. Mouth opening central, 

 anal pore small, submarginal to inframarginal. Ambulacral fur- 

 rows distinct, sending out two branches a little over half way 

 from the mouth to the margin. The main ambulacral furrows 

 continue on the upper surface, passing through the middle of the 

 petals to the apical system. The branching furrows continue 

 across the margins to the upper surface, running over the middle 

 portion of small ridges which extend half way from the margin 

 to the apical system, along the line of junction of the ambulacral 

 and interambulacral plates. 



Apical system central, slightly sunken. Ambulacral star sym- 

 metrical, petals raised, wide open at the ends, and continuing to 

 the margin. Inner rows of pores almost parallel for last three- 

 fourths of their length, diverging slightly near the margin. 

 Outer rows diverging for about half the distance to the margin; 

 from here to the margin they contract gradually toward the inner 

 rows. Near the margin the pores are almost in the middle of the 

 ambulacral plates. Interporiferous area, forming almost two- 

 thirds of the width of the petal. Middle of the interambulacral 

 area occupied by a wide depression extending from margin to 

 apical system. Lesser depressions in the ambulacral areas be- 

 tween the two small ridges and the petals, extending half way to 

 the apical system. 



Tubercles on abactinal surface large on ridges and in inter- 

 poriferous area, irregular in size and spacing; on actinal surface 

 large and regularly spaced. 



Dimensions: Longitudinal diameter 62 mm. 



Occurrence : Salinas Valley, Monterey County. 



This variety differs from typical Astrodapsis antisclli in hav- 

 ing a markedly thin edge, in having the petals raised somewhat 

 higher, and in having the arch of the abactinal surface commence 

 some distance in from the edge, and not at the margin of the test. 



Astrodapsis antisclli shows quite a wide variation, most notice- 

 able in the thickness of the edge of the test, and the degree to 

 which the petals are raised. With more material available it will 

 probably be found desirable to form several varieties. A very 



