96 



University of California Puhlications in Geology [Vol. 12 



ASTRODAPSIS COALINGAENSIS Kew, n. sp. 

 Plate 16, figures 2a, 2b 



Holotypc.—No. 11355 Univ. Calif. Coll. Invert. Pal. 



Test large. Measurements of specimen 11355 : anteroposterior 

 diameter 83 mm., transverse diameter 82 mm., greatest height 13.5 mm. 

 Outline subeireular, with distinct notches in the ambulacral areas, 

 those in the posterior areas being larger than the others; the margin 

 also may be slightly indented at the junction of the two areas; margin 

 and submarginal area markedly thin relatively, especially in the larger 

 specimens. Test much depressed and rising gently to a central apex, 

 the major part of the elevation taking place within the area limited 

 by the length of the petals. Apex either coincides with the apical 

 system or is immediately anterior to it. Apical system small and 

 central. Ambulacral star symmetrical. Madreporite subpentagonal, 

 with four genital pores, the odd posterior one being absent ; five per- 

 forated radial plates present. Ambulacra wide, being broader than 

 the interambulacra at the margin. Dorsal portions petaloid. Petals 

 similar, moderately wide, and extending about two-thirds the distance 

 to the margin; wide open at their extremities; slightly tumid, the 

 tumidity becoming more pronounced toward the apical system ; inner 

 rows of rounded pores extend in slightly divergent lines, not con- 

 tracting toward the ends of the petals except in occasional specimens, 

 and in such individuals the convergence is barely perceptible ; outer 

 rows of elongate jiores diverge more than the inner rows, and when 

 about half way to the margin converge close to the inner rows, con- 

 tinuing in this manner to the ends of the petals ; a few sporadic pores 

 extend beyond, nearly to the margin. Poriferous areas equal about 

 seven-tenths the interporiferous area in the lateral petals; poriferous 

 area somewhat narrow^er in the odd anterior petal, caused by a slight 

 narrowing of the petal. Interambulacral areas nearly flat, but with 

 very faint, broad depressions. Inferior surface somewhat concave to 

 the peristome. Ambulacral furrows distinct, extending from the peris- 

 tome to the margin as a straight line and often continuing over the 

 upper surface as a median line on the petals. Peristome subeireular, 

 central, and sunken. Perii^roct inframarginal, round, small, and situ- 

 ated at or very near the margin. Tubereulation not regular ; tubercles 

 on petals relatively large and i^rominent ; on the surface between the 

 petals they are much smaller, becoming very fine and indistinct near 

 the median line of the interambulacral areas ; those on the under side 

 as large as those on the petals. 



