1915] 



Keiv: Echinoids of San Pablo Group 



369 



S. gabbi, 



S. gabbi n. var. tenuis S. fairbanksi 



Average length of odd anterior petal 



; — ==.6905 .674 .5945 



Average distance from apical system to ambitus 



The ratio of the length of the petals of the bivium to the distance 

 from the apical system to the ambitus shows similar results. 



Occurrence. — Lower San Pablo group immediately above the basal 

 beds. 



Average measurements. — Anteroposterior diameter, 33.5 mm. ; 

 transverse diameter, 34.5 mm. ; greatest thickness, 5.8 mm. 



SCUTELLA PABLOENS1S, n. sp. 

 Plate 39, figures 6a, 66 



Test thin ; transverse diameter usually greater than the antero- 

 posterior diameter ; posterior interambulacral area strongly lobed ; 

 ambitus notched in the ambulacral areas. Summit anterior to apical 

 system, the latter being central. Interambulacral areas flat. Ambu- 

 lacra petaloid ; petals slightly elevated and wide open. Pores conju- 

 gate; inner rows of rounded pores extend in almost straight lines to 

 the ambitus, converging slightly to a point two-thirds the distance to 

 the margin, whence they diverge to the ambitus ; outer rows of 

 elongated pores converge markedly toward the same point, where they 

 become rounded and continue parallel with the inner rows to the 

 margin. Anus marginal. Inferior surface slightly concave. Ambn- 

 lacral furrows are present and extend undivided to the margin of the 

 test. Tubercles small and numerous. 



Scutella pabloensis differs from Astrodapsis tumidus Remond 

 mainly in its comparatively thinner test. The transverse diameter is 

 greater than the anteroposterior diameter, while in the latter the con- 

 trary is true. The petals are not so markedly elevated and no inter- 

 ambulacral depressions are present. The petals are more strongly 

 constrieted about two-thirds the distance to the margin. From 

 Astrodapsis tumidus, n. subsp. cierboensis, it differs mainly in that its 

 transverse diameter is greater than the anteroposterior diameter; the 

 test is not so thick; and the summit is situated farther toward the 

 anterior margin. 



Occurrence. — Lower San Pablo group in the same beds with Astro- 

 dapsis t. cierboensis. 



Average measurements. — Anteroposterior diameter. 45.8 mm. : 

 transverse diameter, 49.5 mm. ; greatest thickness, 10.0 mm. 



