SUMMARY. 357 



elongated pores placed close together. The single ambulacrum in a long shallow 

 anteal sulcus, with very narrow poriferous zones composed of small round pores disposed 

 apart in oblique, widely separate simple pairs. Oral opening bilabiate, very excentral 

 near the margin. Apical disc small, compact, with four perforated genital plates and 

 five very small oculars. Anal opening oval, high up on the posterior border. Genus 

 Cretaceous. Three British Cretaceous species (pp. 262 — 264). 



Genus 23. — Epiaster, d" Orhigny (p. 265). 



Test thin, oblong, more or less elevated, often cordiform, with small crenulated 

 tubercles apart, furnished with interspaced granules. No fascioles. Antero- and 

 postero-lateral pairs of ambulacra petaloidal and lodged in depressions. Anterior pair 

 longer and more developed than posterior. Poriferous zones equal in each ambulacra, 

 composed of elongated pores, shorter in the internal than the external rows. Single 

 ambulacrum lodged in a well-defined furrow, composed of pores different from those of 

 the antero- and postero-lateral pairs. Oral opening near the anterior border and strongly 

 bilabiate, the inferior lip strong and prominent. Apical disc with four perforated 

 genital and five ocular plates. Anal opening round or oval, situated at the posterior 

 border. Genus confined to Cretaceous strata. Two British Cretaceous species 

 (pp. 265—270). 



Genus 24. — Micraster, Agassiz (p. 270). 



Test thin, cordiform, more or less inflated. Tubercles perforated, crenulated, sparsely 

 distributed on upper surface, larger and closer below. Fascicle subanal, forming a ring 

 around the posterior extremity, embracing half of the upper and half of the lower part of 

 the border. Ambulacral pairs petaloidal, closed at their extremities, the anterior 

 exceeding the length of the posterior pair. Anterior ambulacrum in a wide, shallow 

 furrow, indenting the border of the test. Poriferous zones equal in each ambulacra ; 

 pores oval, joined by transverse depressions. Oral opening transverse, near the border, 

 l)ilabiate with prominent projecting lip. Apical disc small, central, solid, composed of 

 four perforated ovarial and five perforated ocular plates. Madreporiform body small, 

 located in the middle of the disc. Anal opening oval in the upper part of the border 

 under a ridge-like projection of the dorsal surface. Spines small, acicular. Genus found 

 in Cretaceous strata. Four British Cretaceous species (pp. 271 — 280, 335 — 340). 



Genus 25. — Echinospatagds, Breynius (p. 280). 



Test thin, cordiform, granulated, more or less inflated above, flattened below. 

 Fascicle absent. Tubercles of various sizes, crenulated, most numerous at the anterior 



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