1920] 



Kew: Cretaceous and Cenozoic Echinoidea 



93 



ASTRODAPSIS CALirORNTCUS Kew, n. sp. 

 Plate 18, figure 2 



Astrodapsis whitneyi. Arnold, U. S. Geol. Surv. Bull., no. 396, 1909, p. 63, 

 pi. 9, fig. 1. 



Astrodapsis whitneyi. Arnold, U. S. Geol. Surv. Bull., no. 398, 1910, p. 94, 

 pi. 33, fig. 1. 



Astrodapsis whitneyi. Stefanini, in part, Boll. Soe. geol. italiana, vol. 30, 

 1911, p. 703. 



Astrodapsis arnoldi Twitcliell. U. S. Geol. Surv. Mon., vol. 54, 1915, pp. 

 199-200, pi. 95, fig. 1. 



Holotijpe.—No. 11354 Univ. Calif. Coll. Invert. Pal. 



Test large. Measurements of specimen no. 11354: anteroposterior 

 diameter 85.8 mm., greatest lateral distance from apical system to 

 margin of test 41.3 mm., greatest height 13 mm. Outline from above 

 subeircular. Margin very thin and rounded ; broadly notched in the 

 ambulacral areas, the degree of notching being less prominent in the 

 odd anterior area. Upper surface considerably depressed ; submar- 

 ginal area greatly flattened ; petals rise uniformly to summit, whereas 

 in the interambulacral areas the slope of the surface is more gentle 

 near the margin. Broad, deep depressions exist in the interambulacral 

 areas of the superior surface. Ambulacral areas considerably elevated 

 near the center of the test, but become flattened in the submarginal 

 area. Greatest elevation of the test on the odd anterior petal imme- 

 diately in front of the apical system. Apical system slightly anterior 

 to the center of the test and depressed below the level of the petals. 

 Petals wide, elongate, and nearly reaching the margin, where they are 

 wide open ; width of each poriferous zone equal to half the inter- 

 poriferous area ; inner rows of pores diverge gradually until about 

 one-half the distance to the margin, where they continue in parallel 

 lines close to the margin, near which they again slightly diverge. 

 The initial divergence of the outer rows of pores is greater than that 

 of the inner rows, but when about two-thirds the distance to the 

 margin the outer rows converge close to the inner, continuing so to 

 the margin ; pores conjugated, slit-like, but becoming rounded near 

 the ambitus. Lower surface concave. Peristome small, rounded, and 

 subcentral. Broad, deep, and straight ambulacral grooves extend from 

 the peristome to the margin. Periproct very small, round, and situ- 

 ated close to the margin on the under side. Tuberculation consists of 

 large scrobicular tubercles on the petals with smaller ones on the 

 interambulacral areas ; those on the inferior surface very numerous 

 and about the same size as those on the petals. 



