238 



ECHINODEKMATA ECHINOIDEA SUB-BRANCH in 



more rarely cuts ; one in the median line of the posterior lAmb, the others 



c 



FIG. 383. 

 Scutella subrotundata, Lain. Miocene ; Bordeaux. A, B, Ventral and dorsal aspects. C, Section, Vi- 



in the Amb. Amb petaloid dorsally, the posterior pair the longest. Pliocene 

 and Eecent. 



Lenita, Desor. Eocene. Eotula, Klein. Eecent. Arachnoides, Breyn. 

 (Asterodaspis, Conrad). Pliocene and Recent. 



Order 5. SPATANGOIDA. Duncan. 



" Euechinoidea with an adinal or a frontal peristome, and a periprod situated 

 the dorso-central system, in the posterior interambulacrum ; without external 

 branchiae ; jaws, teeth, and perignathic girdle. Spheridia numerous." Duncan. 



Sub-Order A. CASSIDULOIDEA. Duncan. 



Ambulacra abactinally simple, petaloid or sub-petaloid, usually similar. Some 

 or all of the interambulacra with a single peristomial plate ; the postero-lateral areas 

 symmetrical actinally, without any fusion of plates; no plastrons. Peristome 

 I, with or without floscelles. 



Family 1. Echinoneidae. Wright. 



Test tall, or low and tumid dorsally ; tumid and rarely flat actinally. Apical 

 system central, compact, with four perforated basals. Ambulacra similar, dorsally 

 apetalous or sub-petaloid. Pores in simple pairs or in oblique triplets actinally ; no 

 floscelle. Peristome oblique or transversely elliptical, rarely symmetrical. Periproct 

 actinal, marginal or supra-marginal. Cretaceous to Recent. 



