FAMILIES AND GENERA OE THE MADREPOEARIA. 



129 



Astrseid nature of their type species, Plerastrcea Savignyi, Glaus- 

 astrcea has now to be removed from the true Astrseidse, for it has 

 sjnapticula. Plerastrcea mirahilis, nobis, Foss. Corals &c. of Sind, 

 Pal. Indica, p. 65 (1880), cannot remain in its genus as deter- 

 mined by Milne-Edwards and Jules Haime. It is now Fratzia 

 mirahilis, and a Lophoserine. 



G-enus Pleraste^a, Milne-Edwards Sf Jules Haime^ Rist. Nat. 

 des Cor all. vol. ii. p. 553 (1857). 



Colony massive, turbinate, or flat, with a convex or subplane 

 upper surface. Corallites limited by walls which are simple, 

 united, and well developed. Calicos superficial. Columella 

 papillary. The septa few and subconfluent with those of the 

 neighbouring calices, dentated, uniting more or less. Dissepi- 

 ments well developed and abundant. An epitheca may exist 

 and be strong and folded. 



Distribution. — Fossil. Trias : Europe. Jurassic : England. 

 Eocene : Erance. — Suhfossil. Eed Sea. — Becent. Eed Sea ? 



The next genus is a doubtful one. If it has no synapticula it 

 must remain ; but if it has, it is synonymous with Centrastrcea, a 

 subgenus of Thamnastr(jea, Lesauvage. 



Genus Holoccenia, Milne-Edwards Sf Jules Haime, Brit. Foss. 

 Corals, Pal. Soo. p. 99 (1851). 



Colony massive, gibbous. Corallites united by their costsD, 

 which are slightly developed^ or by their walls. The septa are 

 entire, have their upper edge nearly horizontal, and merge into 

 those of the neighbouring calices by means of the costse, with 

 which they are continuous. These septo-costse hide the summit 

 of the walls of the calices. The columella is styliform. 



Distribution. — Fossil. Cretaceous : Europe, S. India. Eocene : 

 Borneo. 



This is not a satisfactory genus ; see the admirable remarks of 

 *ts founders (op. cit. p. 99, 1851). The South-Indian Cretaceous 

 species has ragged septa and no synapticula. 



XIV. Alliance TABULOIDA. 

 Agglomerate Astrseidee increasing by gemmation. Coralhtes united by 

 their walls. Dissepiments in the form of tabulee. Septa variable, in 

 cyclical arrangement. 



Genus Holocystis, Lonsdale. 

 Genus Coccophyllum, Reuss. 

 Genus absorbed : — Tetraccenia, d'Orb. 



LINN. JOURN. — ZOOLOGY, TOL. XVIIl. 9 



