358 CRETACEOUS ECHINOIDEA. 



border. The pairs of ambulacra petaloidal, unequal in length, large, lodged in a 

 depression. Poriferous zones of the anterior pair longer and wider than the posterior pair. 

 The single ambulacrum lodged in a wide, deep anteal furrow ; its poriferous zones are 

 narrow and equal, and the holes are smaller and placed closer together than the pores in 

 the pairs. Oral opening small, subpentagonal near anterior border. Apical disc com- 

 pact, composed of four finely perforated ovarial plates, and five small oculars with madre- 

 poriform body extending into the centre of the disc. Anal opening oval, placed in the 

 upper part of the posterior border. Spines unknown. Genus found in the Cretaceous 

 strata. Four British Cretaceous species (pp. 281 — 287). 



Genus 26. — Enallaster, iTOrhigny (p. 288). 



Test thin, cordiform, tubercles small, chiefly developed on sides and base. Ambu- 

 lacral summit subcentral. Ambulacral pairs subpetaloid, unequal, and depressed. Pori- 

 ferous zones in the anterior pair unequal. The posterior zones much larger and wider 

 than the anterior zones. Single ambulacrum wider than laterals, in a wide anteal 

 furrow with narrow poriferous zones, and pores arranged obliquely. Oral opening sub- 

 pentagonal near anterior border. Apical disc small, with four perforated ovarial and 

 five perforated ocular plates. Anal opening oval, at summit of truncated posterior 

 border. Genus found in the Lower-Cretaceous strata. Two British Cretaceous species 

 (pp. 288—292). 



Family X.— ECHINOCORID^, Wright (p. 292). 



Test thick or thin, oval, cordate or conoidal, furnished with irregular small perforated 

 tubercles. Sometimes a marginal fasciole. Ambulacral areas equal, narrowly lanceolate, 

 converging to the vertex. Poriferous zones narrow; pores disposed in pairs at a 

 distance apart. Oral opening transversely oblong, often bilabiate near the anterior 

 border. Apical disc small or large, narrow and elongated, having four perforated and 

 one unperforated ovarial plate with five perforated oculars. Anal opening round' 

 marginal, or supra-marginal. Spines small. Range of family from the Lower 

 Cretaceous to the existing period. Four genera : Cardiaster, Intulaster, Holaster, 

 EcHiNOcoRYS, with sixteen species (pp. 293 — 334). 



Genus 27. — Cardiaster, Forles (p. 293). 



Test thin, cordiform, upper surface convex, anteal furrow well-marked with angulated 

 borders. Tubercles perforated, raised upon crenulated bosses and surrounded by areolae. 

 A fasciole passing beneath the anal opening and continued on the sides. Oral opening 



