1920] Kew: Cretaceous and Cenozoic Echinoidea 103 



the interporiferous area. Pores conjugate. Inferior surface nearly 

 flat in the submarginal area, but markedly concave around the peris- 

 tome. Ambulaeral furrows broad, deep, extending to the margin, and 

 throwing off a pair of faint lines slightly over one-half the distance to 

 the edge of the test ; the main furrows continue through the marginal 

 notches on the upper surface, and form a shallow median groove on 

 the petals. Tuberculation prominent on unweathered specimens ; con- 

 sists of scrobicular, perforated tubercles of moderate size ; similar on 

 both surfaces except in the interambulacral depression on the abactinal 

 side, where they are somewhat smaller. Peristome round, sunken, 

 posteriorly slightly eccentric or central. Periproct small, round, in- 

 framarginal, and situated on the lower surface a distance equal to its 

 own diameter from the edge of the test. 



Belated forms. — This species is closely related to Astroclapsis 

 tumidus Remond, being one of the most highly developed members in 

 this evolutionary series. It may be distinguished from the latter by 

 its uniformly greater size, thicker margin, deeper interambulacral 

 grooves, usually more elevated petals, and more deeply concave inferior 

 surface. It is most closely allied to A. arnoldi peltoides (Anderson 

 and Martin), differing in that it lacks the marked grooves in the am- 

 bulaeral areas along the sides of the petals ; and in that the petals 

 are usually wider. It may be separated from A. arnoldi (Pack) in 

 lacking the grooves along the sides of the petals ; in that the poriferous 

 areas of the petals are narrower ; in lacking the usually characteristic 

 bell-shaped appearance of A. arnoldi, and in that the lower surface 

 is much more strongly concave. A. margaritanus Kew differs in 

 having a markedly depressed test and in that the petals are not so 

 highly elevated. 



Geologic horizon. — Uppermost San Pablo group, above the fresh 

 water horizon of this series, Lower Pliocene ; probably equivalent to 

 Lower Etchegoin (Jacalitos). 



Localities. — San Pablo Bay-Mount Diablo region of Middle Cali- 

 fornia. Cotypes from Univ. Calif, loc. 1742. 



ASTEODAPSIS MAEGARITANUS Kew, n. sp. 

 Plate 22, figures lo, Ih 



Cotypes.— Nos. 11023 and 11035 Univ. Calif. Coll. Invert. Pal. 



Size moderate. Average measurements of specimen 11023: antero- 

 posterior diameter 61.5 mm., transverse diameter 52.6 mm., greatest 

 height 11.5 mm. ; of specimen no. 11035 : anteroposterior diameter 58.7 



