ORDER IV EUECHINOIDEA—CLYPEASTROIDA. 235 
rather flat actinally. 4mb long, open, with broad poriferous zones nearly to 
ambitus, narrowing thence to peristome. Pores wide apart and in pairs where 

Fic. 378. 
Conoclypeus conoideus, Goldf. sp. Eocene; Kressenberg, Bavaria (2/3 natural size). 
the zones are broad ; the pairs separated by costae. Pores continued in single 
series over the ambitus as far as the central, pentagonal peristome. Periproct 
infra-marginal, oval (?). Cretaceous ; Eocene. 
Galeropygus, Cotteau ; Pachyclypeus, Desor. Upper Jura; Europe. 
Order 4. CLYPHASTROIDA. Duncan. 
“ Huechinoidea with an actinal peristome, a periproct situated beyond the dorso- 
central system, in the posterior interambulacrum ; with external branchiae ; with 
tentacular pores in the interambulacra, and more than a pair to an ambulacral 
plate ; tentacles heteropodous in arrangement; with more or less horizontal and 
rarely vertical teeth, and with jaws situated superiorly to the disconnected perignathic 
girdle. Spheridia few, covered.”—Dunean. 
Family 1. Fibulariidae. Gray (emend. Duncan). 
Test small, with rudimentary, widely open, few-pored petals. Interambulacra 
small, with a single apical and a single peristomial plate. Ambulacra limited 
actinally on the interior of the test by low vertical partitions at their sides, radiating 
toward the peristome. Perignathie processes broad, low, one on each interambu- 
lacrum. Periproct usually actinal. Cretaceous to Recent. 
Echinocyamus, van Phels. Test thick, depressed, pyriform or sub-circular 
in outline, concave actinally. Amb broader than the Ldmb), short where 
slightly petaloid, widely open distally ; pairs of pores few and increasingly 
