1920] Kew: Cretaceous and Cenozoic Echinaidea 



67 



Test of medium size. Measurements of specimen 11017 : antero- 

 posterior diameter approximately 49 mm., transverse diameter 53.7 

 mm., greatest height 5.2 mm. Outline subcircular to transversely sub- 

 oval, usually with broad, indistinct marginal notches in the ambu- 

 lacral areas ; test greatly depressed, with margin markedly thin. 

 Apical system anteriorly eccentric. Upper surface arched to a low 

 summit, which is forward of the apical system and relatively close 

 to the anterior margin. Apical star comparatively small ; madreporite 

 large and pentagonal in shape ; four genital pores present, the odd 

 posterior one being absent. Ambulacra broader than the interambu- 

 lacra at the ambitus. Ambulacral areas widen rapidly from the ends 

 of the petals to the margin, but the interambulacral areas maintain a 

 uniform size from that point to the edge of the test. Abactinal portion 

 of the ambulacra petaloid. Lateral petals narrow and subelliptical 

 in outline ; both rows of pores converge slightly toward the distal end 

 of the petals, the convergence of the outer rows being greater than 

 that of the inner rows. Poriferous areas wide, and nearly as broad 

 as the interporiferous area. Odd anterior petal distinctly different 

 from the others ; much broader, with a greater width of the inter- 

 poriferous area and slightly elevated ; inner rows of pores diverge 

 somewhat near the distal end of the petal, and the outer rows converge 

 but slightly if at all. A few pairs of pores in divergent rows continue 

 for a short distance beyond the ends of all the petals. Pores in all 

 petals oval in shape and conjugated. Very small scrobicular tubercles 

 are crowded over both surfaces, but become larger and less numerous 

 near the peristome. Inferior surface fiat, with deep ambulacral fur- 

 rows which extend in wavy lines from the peristome to the margin ; 

 they have a slight tendency to branch near the edge of the test. 

 Peristome round, small, and slightly eccentric anteriorly. Periproet 

 round, small, supramarginal, and situated about its own diameter 

 from the edge of the test. 



Belated forms. — Scutella fairhanl'si differs from 8. gahbi (Re- 

 mond), to which it is closely allied, in that it attains a much greater 

 size and has slight marginal notches in the ambulacral areas ; in 

 having deeper ambulacral furrows on the inferior surface ; in that 

 the periproet is entirely supramarginal, the test relatively thinner, 

 and the submarginal area of the upper surface comparatively broader. 

 "With the exception of the difference that the margin is notched, these 

 distinguishing characters separate it from the large form and notched 

 form of 8. gahhi. S. gabhi var. tenuis Kew differs in being of smaller 



