90 University of California Puhlications in Geology [Vol.12 



center of the test and situated on the odd anterior petal. Apical 

 system small and placed very slightly to the posterior of the center 

 of the test. Ambulacra much wider than the interambulacra, the latter 

 being about five-eighths the width of the ambulacra. Petals markedly 

 broad, wide open, and extending to the edge of the test. Odd anterior 

 petal somewhat narrower than the paired petals. Both the inner and 

 outei' rows of pores diverge for about one-third tlieir length, converge 

 until about three-fourtlis the distance to the margin, and then again 

 diverge to the edge of the test ; the divergence of the outer rows 

 slightly greater than that of the inner rows, and the poriferous areas 

 gradually narrowing until the two rows are practically united at the 

 margin. Interporiferous areas exceptionally broad, being about three 

 and a-half times the width of each poriferous area. Rows of pores 

 in the odd anterior petal diverge to their maximum, and then continue 

 in nearl.y parallel lines to the margin, converging but little ; both 

 tlie poriferous area and interporiferous area nari'ower than in the 

 paired petals ; interporiferous area four times the width of each porif- 

 erous area. Abactinal surface of the interambulacra characterized 

 by broad, deep depressions extending from the apical system to the 

 ambitus. Indistinct, broad grooves are present along the margins of 

 the petals. Inferior surface slightly concave. In the single specimen 

 at hand the under side is imperfectly exposed. No ambulacral fur- 

 I'ows are shown, but branching lines are present which pass to the 

 abactinal side and form a median ridge on the petals and sutui'al lines 

 between the ambulacral and interambulacral areas. Periproct rela- 

 tively small and inframarginal ; situated about its own diameter from 

 the edge of the test. Tuberculation consists of well defined scrobic- 

 ular tubercles of fairly large and uniform size over both surfaces. 



Related forms. — This form may be easily distinguished from all 

 other similar types by its markedly wide petals, greatly depressed test 

 with thickened margin, and apparent lack of ambulacral furrows; 

 if present they are not well developed. It closely resembles Astro- 

 daixsis antiseUi Conrad and other forms of the Upper San Pablo group 

 (Santa Margarita), but may be separated by its broad, flattened test 

 and more prominent interambulacral grooves. 



Geologic horizon. — Lower Etchegoin (Jacalitos) formation. Lower 

 Pliocene. 



Loeality. — Near Standard Oil Company's well "Powell No. 1," 

 Sargent Canyon, east side of Salinas Valley, Priest Valley quadrangle, 

 California (Standard Oil Co. loc. 41), Univ. Calif, loc. 3572. 



