FAMILIES ATSTD GENERA OE THE MADREPORAHIA. 119 



Group-Genus Eeptastr^a. 



Grenus Lbptaste^Aj Milne- Edwards Sf Jules Haime, Hist. Nat. 



des Corall. vol. ii. p. 493 (1857). 



The colony is massive, or else incrusts, and is subplane or 

 convex at the free surface. Corallites short, with very dense 

 muro-costal structures, which become compact and fused. Calices 

 with distinct margins, close, shallow. Columella papillary. 

 Septa thin, close, exsert, margin subentire, granular; inner 

 edge trabeculate, vsdth ascending denticles. Costae small, visible 

 between the calices. Endotheca feeble. Gremmation extracali- 

 cular ; sometimes fissiparity occurs. 



Distribution. — Becent. Indian Ocean and Eed Sea. 



It appears that the incrusting species extends by a kind of 

 stoloniferous gemmation. — Duncan, Proc. Linn. Soc. 1884. 



IX. Alliance BARYSASTR^OIDA. 



Agglomerate Astraeidse, increasing by marginal and submarginal (within 

 the calice) gemmation. Walls fused, but thick, and often subcellular. 

 Septa denticulate. 



Genus Barysastr^ea, Ed. & H. 



Genus Acanthastr^a, Ed. & H. 



Grenus BAETSASTE-aEA, Milne-Edwards and Jules Haime, Hist. 

 Nat. des Corall. vol. ii. p. 312, pi. D 8. fig. 2 (1857). 

 The colony is convex or subgibbous, very dense and compact. 

 The corallites are united by their very thick and solid walls. 

 Calices shallow, close, small, polygonal, and barely separated by 

 shallow grooves. Columella subpapillary above, compact and 

 large low down. Septa very thick, close, and not much toothed. 

 Endotheca slightly developed. Internal cavity gradually filling 

 up inferiorly. Gremmation submarginal. 

 Distribution. — Recent. Locality ? 



G-enus Acakthastr^a, Milne-Edwards Sf Jules Haime, Hist. 

 Nat. des Corall. vol. ii. p. 501, pi. D 6. fig. 1 (1857). 

 The colony is in the shape of a subplane or convex mass. The 

 corallites, short or tall and broad, are united by their walls which 

 are subcellular. Calices subpolygonal, with broad spinous mar- 

 gins, with or without irregular superficial grooves. Columella 

 parietal or rudimentary. Septa exsert, stout, and much spined, 

 the largest of the spines being the most external. The upper 

 part of the lamina is trabeculate below the spinous teeth. Endo- 



