1915] 



Kew: Echinoids of San Pablo Group 



371 



Pores conjugate. Inner rows of rounded pores contract slightly about 

 two-thirds the distance from the apical system to the margin ; outer 

 rows of elongated pores also converge close to the inner rows at the 

 same place and then continue to the ambitus parallel with the inner 

 rows ; in some cases the pores extend on the under surface. Anus 

 marginal. Inferior surface concave, with no ambulacral furrows, 

 except in occasional specimens where broad indistinct grooves and 

 bifurcating ambulacral lines are present, the latter extending on the 

 upper surface. 



Astrodapsis tumidus, n.subsp. cierboensis shows distinct intergra- 

 dational characters between 8cutella(?) breweriana Remond and 

 Astrodapsis tumidus Remond. Astrodapsis I. cierboensis is dis- 

 tinguished from Scutella(t) breweriana mainly by its raised petals; 

 but specimens of the latter sometimes have this character. Both forms 

 have a tendency to take an elliptical shape, and the petals have wide 

 poriferous areas. In no case does Scutella( f) breweriana have inter- 

 ambulacral depressions, while a few specimens of Astrodapsis t. 

 cierboensis possess incipient ones. 



The main differences between Astrodapsis t. cierboensis and Astro- 

 dapsis tumidus are, that the margin is much thicker in the former; the 

 ambitus is not so strongly notched in the ambulacral areas ; the petals 

 and poriferous areas are usually broader ; the interambulacral depres- 

 sions are absent or slight ; the ambulacral furrows are very indistinct 

 or absent ; and the tubercles are not so prominent. It also differs from 

 Scutella pabloensis, n. sp., in that the margin of the latter is more 

 strongly notched and thicker, and the test has larger tubercles. 



Occurrence. — Lower San Pablo group above the lower Scutella 

 gabbi zone. It is found with Scutella pabloensis, n. sp. It also oc- 

 curs in the lower part of the Santa Margarita formation. 



Average measurements. — Anteroposterior diameter, 36 mm. ; 

 transverse diameter, 32 mm. ; greatest thickness, 9.5 mm. 



ASTEODAPSIS ALTUS, n. sp. 

 Plate 40, figures 3a, 3b 



Test sub-circular to sub-pentagonal in outline ; margin thick • 

 superior surface rising immediately from the ambitus to the summit, 

 which is comparatively high and is anterior to the apical system, thus 

 giving the test a distinctly conical shape. Ambitus slightly notched in 



