ORDER V EUECHINOIDEA—SPATANGOIDEA 243 
Amb in a groove, with small, simple, distant pairs of pores ; the other Amb 
flexuous, with comma-shaped pores placed obliquely to one another. Periproct 
supra-marginal. Upper Jura and Lower Cretaceous. 
Sub-Order B. SPATANGOIDEA. Duncan. 
Peristome eccentric in front, rarely pentagonal in the adult, usually with a 
posterior labrum, behind which is a long plastron bounded laterally by the posterior 
ambulacra. Ambulacra dissimilar. Interambulacra with a single plate at the 
peristomial margin, the postero-lateral areas usually unsymmetrical actinally. 
Fascioles present or absent. 
Family 1. Ananchytidae. Desor. 
Test ovoid or sub-cordiform in marginal outline, tall or depressed, and with large 
plates. Ambulacra in a bivium and trivium, nearly similar, flush, apetalous ; pairs 
of pores largest near the apex and at the peristome, may be uniporous.  Periproct 
variable in position. Cretaceous to Recent. 
Echinocorys, Breyn. (Ananchytes, Mereati), (Fig. 392). Test large, oval in 
marginal outline; high, rounded, or keeled apically, flat actinally. Amb 
biporous, the pairs of pores well 
developed abactinally, but becom- 
ing smaller, closer, and oblique 
toward the ambitus, where they 
are more distant. Posterior Amb 
actinally long and broad, the pairs 
small, and pores oblique. Peri- 
stome oval, broader than long. 
Periproct infra -marginal, pos- 
terior, oval. Apical system elon- 
gate. Very abundant in the 
Upper Cretaceous. £. ovata, 
Leske sp., often attains a very 
large size. 
Holaster, Ag. (Fig. 393). Test 
ovoid in marginal outline, flat 
actinally, tumid and high abactin- 
ally. Anterior dmb in a shallow 
groove. Peristome _ elliptical, 
broadest transversely. Periproct 
supra-marginal, oval. Apical 
system elongate. Cretaceous and 
Miocene. 


Fic. 392. 
Offaster, Desor. Test small, Echinocorys ovata, Leske sp. White chalk ; Haldem, West- 
tumid. Anterior Amb sometimes phalia. A, B, Profile and ventral view, 1/3. C, Dorso-central 
: system, enlarged. D, Portion of Amb and [Amb areas, 1/). 
in a shallow groove. Peristome 
oval, broadest transversely. Periproct supra-marginal, circular or ovoid. 
Apical system elongate. Cretaceous. 0. pilula, Ag. sp. 
Hemipneustes, Ag. Test large, ovoid in marginal outline, high and tumid 
dorsally, flat actinally. Anterior Amb in a deep, narrow groove extending to 
