1920] 



Kew: Cretaceous and Cenozoic Echinoidea 



105 



ASTEODAPSIS OENATUS Kew, n. sp. 

 Plate 21, figures la, lb, Ic, Id 



Cotypes.—Nos. 11374 and 11375 Univ. Calif. Coll. Invert. Pal. 



Test of medium size. Measui'ements of specimen no. 11374: antero- 

 posterior diameter 44.7 mm., transverse diameter 42.7 mm., greatest 

 height 11 mm. Outline from above subpentagonal ; margin thick and 

 notched in the ambulacral areas, the notching being greater in the 

 two posterior ones. Apical system symmetrical and eccentric to the 

 anterior. Upper surface distinctly elevated, giving the test a broadly 

 subconical shape. The apex is immediately anterior to the apical 

 system. Ambulacral areas broader than the interambulacral areas 

 at the margin ; ambulacra petaloid. Petals considerably elevated, 

 narrow, and wide open at their extremities. Inner rows of rounded 

 pores after reaching their fullest divergence continue in straight lines 

 to the ends of the petals, with no tendency to converge ; outer rows 

 of transversely elongate pores when about one-half the distance to the 

 margin converge close to the inner rows, and then continue parallel 

 with the latter to the end. Due to the slight eccentricity of the apical 

 system the petals of the trivium extend nearly to the margin, the odd 

 anterior one reaching the edge of the test, while those of the bivium 

 extend a little over three-fourths the distance to the margin. Inter- 

 ambulacral plates on the upper surface are heavy, large, and orna- 

 mented by greatly swollen edges, and in the center of the depressed 

 portion of the plate by a small elevation, or boss, which corresponds 

 in shape to the plate itself ; the ambulacral plates of the upper surface 

 are swollen along their edges, the enlargement being greater at their 

 junction with the plates of the interambulacra, so that it gives the 

 appearance of a double line extending along the suture from the 

 margin toward the apical system. All the plates of the under surface 

 possess a thickened border. This ornamentation is only visible in 

 specimens which have been slightly weathered, and is a very dis- 

 tinctive feature. The inferior .surface is markedly concave, and with 

 deep, broad, undivided ambulacral furrows extending from the peris- 

 tome to the margin. Peristome small, central, or slightly eccentric 

 to the posterior. Periproct small, round, and situated close to the 

 edge of the test on the lower surface. 



Belated forms. — Astrodapsis oniatus is closely related to the otlier 

 species of this genus occurring in the Upper San Pablo group (Santa 

 Margarita formation). It closely resembles A. tumidus Remond, with 



