1920] Kew: Cretaceous mid Cenozoic E chinoideu 75 



SCUTELLA NOREISI Pack 

 Plate 10, figures la, lb 



Scutella (?) norrisi Pack, Univ. Calif. Publ. Bull. Dept. Geo!., vol. 5, 1909, 

 pp. 277-278. 



Scutella 7iorrisi Pack, Univ. Calif. Publ. Bull. Dept. Geol., vol. 7, 1913, 



pp. 299-300, pi. 15, fig. 1. 

 Echiiwrachniits norrisi. Stefanini, Boll. Soc. geol. ital., vol. 30, 1911, p. 703. 

 ScuteUa norrisi. Clark and Twitchell, U. S. Geol. Surv. Mon., vol. 54, 1915, 



pp. 186-187, pi. 85, fig. 9. 



Holotype. — No. 11028 ; Icctotype, specimen no. 11027, Univ. Calif. 

 Coll. Invert. Pal. 



Test large. Measurements of specimen no. 11027 : anteroposterior 

 diameter 73 mm., approximate transverse diameter 98 mm., greatest 

 height 7 mm. Marginal outline, in general, subcircular to subpen- 

 tagonal, but very irregular, due to the presence of broad, deep mar- 

 ginal notches in the ambulacra, the two posterior ones being much 

 greater than the anterior ones ; this gives the test the appearance 

 of a maple leaf ; the margin is also cut by slight indentations at the 

 sutures between the ambulacral and interambulacral areas. Test very 

 thin, with abaetinal surface greatly depressed and rising but little to 

 the apex, which coincides with the apical system. Apical system 

 eccentric slightly to anterior of the center of the test. Madreporic 

 area large, pentagonal, and with four genital pores situated at each 

 of the corners, excepting the odd posterior one. Ambulacra about 

 two-thirds the width of the interambulacra at the ambitus. Ambu- 

 lacra petaloid. Petals symmetrical, of the same length, and extending 

 about three-fifths the distance to the margin ; those of the bivium 

 slightly narrower than those of the trivium. Rows of pores extend 

 in divergent lines for about two-thirds the length of the petal, and 

 then converge very slightly to the end, which gives the petal a nearly 

 wide open appearance ; each poriferous area equal to about one-third 

 the width of the interporiferous area. Petals of small specimens are 

 slightly tumid. Inferior surface faintly concave to the mouth. Peris- 

 tome small, subcircular, and subcentrally located. Broad, deep, 

 straight ambulacral furrows extend to the margin ; indistinct branches 

 are given olf about two-thirds the distance to the edge of the test. 

 Periproct small, I'ound, and inframarginal, almost marginal. 



Related fonm. — Scutella norrisi is one of the most distinctive 

 Lower Miocene echinoids of California. It resembles 8. andersoni 



