1920] 



Kew: Cretaceous and Cenozoic Echinoidea 



99 



Cotijpes.—Nos. 11402 and 11377 Univ. Calif. Coll. Invert. Pal. 



Test of medium size. Measurements of specimen no. 11042: an- 

 teroposterior diameter 51.3 mm., transverse diameter 39.3 mm., great- 

 est height 8.7 mm. Outline suboval, with some forms markedly elong- 

 ate longitudinally ; upper surface much depressed. Margin thickened 

 and rounded ; posterior interambulacral area slightly pointed. Apical 

 system somewhat eccentric to the anterior, with sunnnit of the test 

 immediately forward of the former. Ambulacra almost twice as wide 

 as the interambulacra at the margin ; ambulaeral areas petaloid. 

 Petals large, considerably elevated ; those of the bivium somewhat 

 longer than those of the triviura. All wide open and reaching to 

 the margin. Inner rows of rounded pores at first diverge, when about 

 half the distance to the margin converge very slightly, and then diverge 

 again near the edge of the test, continuing in this manner to the 

 ambitus ; outer rows of elongate pores, more divergent from the begin- 

 ning of the petal, converge to a greater degree when half way to the 

 margin, and then continue parallel with the inner rows. Poriferous 

 areas narrow, with a corresponding very wide interporiferous area, 

 the latter being about four times the width of the former. Interambu- 

 lacral areas possess broad, distinct depressions which extend from 

 the apical system to the margin. Tubercles prominent ; primary 

 tubercles large, not numerous, and lacking on the depressed portions 

 of the test ; placed in well defined scrobicules ; a few secondaries are 

 present, and milliaries are numerous in the intervening spaces. 

 Tubercles of the same size on both upper and lower surfaces, but the 

 primaries more numerous on the actinal side. Inferior surface gently 

 concave ; ambulaeral furrows not distinct, but when present are 

 straight, undivided, and extend but a short distance from the peris- 

 tome, gradually passing into lines which continue on the upper surface 

 to form median lines on the petals. Peristome large, round, slightly 

 sunken, and central. Periproct large, oval, inframarginal, and situ- 

 ated its own diameter from the edge of the test. 



Related forms. — Astrodapsis fernandoensis is unlike ony other 

 species of this genus on account of the presence on the test of the 

 prominent tubercles, which are relatively much larger than those 

 possessed by other forms. This characteristic serves to distinguish it 

 readily from A. cierboensis (Kew) and A. antiselU Conrad, with which 

 it might be confused. 



Geologic horizon. — Lower part of the Fernando formation. Lower 

 Pliocene. 



