1920] Kew: Cretaceous and Cenozoic Echinoidea 107 



the petals flat. Inferior surface slightly concave. Prominent, broad 

 ambulacral furrows are present, which extend undivided from the 

 peristome to the margin. Peristome small, subcircular in outline, and 

 central. Periproct small, round, and placed in a small notch in the 

 margin. Tubercles scrobicular, very small, numerous, and similar 

 on both sides of the test. 



Related, forms. — Astrodapsis (f) pabloensis (Kew) may be dis- 

 tinguished from the forms of the Astrodapsis tumidus group by its 

 much thinner and more depressed test, and by the posterior lobing 

 of the margin. It differs from Scutella fairhaiiksi Arnold in that the 

 petals are narrower and extend nearer the margin, and in that the 

 anus is marginal, and not supramarginal as in *S'. fairhanksi. Scutella 

 gahbi Remond {large form) somewhat resembles it, but differs in lack- 

 ing raised petals. 



Geologic horizon. — -Above the Scutella gabbi zone. Lower San 

 Pablo group, Upper Miocene. Associated with Astrodapsis cierhoensis 

 (Kew). 



Localities. — Holotype from south of San Pablo Bay, near Hercules, 

 Univ. Calif, loc. 232 ; near Layfayette, Contra Costa County, Cali- 

 fornia ; south side of Mount Diablo, Contra Costa County, California. 



ASTRODAPSIS SCUTELLIFORMIS Kew, h. sp. 

 Plate 21, figure 2 



Holotype.— ^0. 31048 Univ. Calif. Coll. Invert. Pal. 



Test much depressed and rather small. Measurements of holotype : 

 anteroposterior diameter 27.3 mm., transverse diameter 25.0 mm., 

 greatest height 5 mm. Outline subcircular, with marginal notches 

 at the ambitus in the ambulacral areas, the posterior ones being more 

 prominent than the others; test relatively thick in the smaller speci- 

 mens, with the margin markedly so. Apex central and coinciding 

 with the apical system. Petals broad, nearly symmetrical, extending 

 close to the margin ; inner rows of pores do not tend to converge, 

 but continue in approximately parallel lines for two-thirds the dis- 

 tance to the margin, where they assume a greater angle of divergence 

 which continues to their end ; the outer rows diverge more at first, 

 but when two-thirds of the distance to the margin converge close to 

 the inner rows and continue so to the end of the petal. Width of 

 poriferous areas equal to three-fifths that of the whole petal ; petals 

 very slightly raised. Ambulacra somewhat wider than the interam- 

 bulacra at the margin. The under surface not well exposed ; slightly 



