NO. 3 CASSIDULOID ECHINOIDS — KIER I23 



PETALOBRISSUS AMMONIS (Fourtau) 

 Plate 16, figures 7-9; text figure 103 



Echinobrissus amvionis Fourtau, 1914. Cat. invertebres foss. figypte, terr. 

 Cretaces, echinodermes, p. 49, pi. 4, figs. 8, 9. 



Material. — I studied Fourtau's figured specimens. The specimen 

 figured in his plate 4, figure 9, is herein designated the lectotype. 

 Both specimens are poorly preserved, being partially silicified and 

 fractured. 



Shape. — Small, lectotype 20.4 mm. long, paratype 25.5 mm. ; elon- 

 gate, anterior margin smoothly rounded, posterior, blunted to shghtly 

 grooved; greatest width posterior to center; adapical surface inflated 

 along median with greatest height at apical system or posterior, sides 

 sloping gently to margin ; adorally very depressed. 



Apical system. — Anterior, apparently tetrabasal but sutures not 

 clear due to silicification ; madreporite large, extending posteriorly 

 separating posterior ocular plates, occupying large central area ; four 

 genital pores. 



Ambulacra. — Petals broad, well developed, equal, lanceolate, tend- 

 ency to close distally, interporiferous zones at greatest width twice 

 width of poriferous zones, tapering distally; poriferous zones with 

 greatest width at midlength, pores conjugate, outer pore elongated, 

 situated oblique to round inner pores. 



Periproct. — Supramarginal, opening approximately two-thirds dis- 

 tance from apical system to posterior margin, in deep narrow groove 

 extending to margin. 



Peristome. — Anterior, deeply depressed, pentagonal, slightly higher 

 than wide. 



Floscelle. — Bourrelets slightly inflated, oblique; phyllodes slightly 

 widened, single pored (text fig. 103) with pores in two series in each 

 half -ambulacrum, approximately eight in each outer series, two or 

 three in each inner ; buccal pores present. 



Tubcrculation. — Owing to poor preservation, details of tubercu- 

 lation not clear. 



Occurrence. — Upper Cretaceous (Turonian), head of Wadi Tarfa, 

 Egypt. 



Location of type specimen. — Lectotype and paratype (25410, F 

 357) in Geological Museum, Cairo, Egypt. 



