1920] 



Ke w : 



Cretaceous and Cenozoic Echinoidea 



87 



ASTEODAPSIS ARNOLDI FEESNOENSIS Kew, n. var. 

 Plate 23, figures 3a, 3b, 3c 



Holotype.—'No. 11032 Univ. Calif. Coll. Invert. Pal. 



Test of medium size. Measurements of holotype : anteroposterior 

 diameter 50.5 mm., transverse diameter 47.3 mm., greatest height 12 

 mm. Outline from above subcireular ; margin thickened and notched 

 in the ambulacral areas, the degree of notching being greater in the 

 two posterior ones. Test somewhat inflated, with the upper surface 

 evenly arched to the summit, which is slightly anterior to the center 

 and near the base of the odd anterior petal. Well marked interam- 

 bulaeral grooves extend from the apical system to the margin, and 

 less prominent grooves are present along the sides of the petals in 

 the ambulacral areas. Apical system comparatively small, and situ- 

 ated in the center of the abactinal surface. Petals of the same size, 

 symmetrical, noticeably narrow, and extending wide open to the 

 margin ; in most specimens they are highly elevated near the apical 

 system, but tend to merge with the general surface near the edge of 

 the test. Poriferous areas narrow, each area being about one-third 

 the width of the interporiferous area. Both inner and outer rows of 

 pores extend in slightly diverging lines for about two-thirds the dis- 

 tance to the ambitus and then the double rows diverge to a much 

 greater degree, giving the distal portion of the petals a flaring ap- 

 pearance. Inferior surface concave. Peristome central, relatively 

 small, and round in outline. Ambulacral furrows deep and broad ; 

 extend undivided to the ambitus and continue through the marginal 

 notches to form faint median grooves on the petals ; about one-half the 

 distance to the margin ambulacral lines are thrown off from the main 

 furrows on the aetinal surface, which extend to the upper surface 

 as sutural lines between the ambulacral and interambulacral plates. 

 Periproct inframarginal, and placed about its own diameter from the 

 edge of the test. Tuberculation consists of small, scrobicular tubercles 

 crowded together over both surfaces. 



Related forms. — This form may be distinguished by its markedly 

 narrow petals, thick test, and small mouth ; these characters separate 

 it from Astrodapsis arnoldi arnoldi (Pack), and from A. major Kew, 

 which seem to be the most closely allied species. 



