FAMILIES AND GENEEA OF THE MADREPOEARIA. 



75 



Solitary genus. 



Genus Hexasmilia, JE. de Fromentel, Pal. Frang.^ Terr. cret. 

 p. 423 (1871). 



Colony fasciculate in close tufts. Corallites free to a great 

 extent, but usually close and polygonal in outline. There are 

 only six septa, which start from the angles of the walls, and one 

 more developed than the others reaches the centre of the calice. 

 Epitheca strong, folded, and reaching to the summit of the 

 colony. 



Bistrilution. — Fossil. Cretaceous : Europe. 

 The genus Isocora, Etallon, is insufficiently determined, and 

 should lapse. 



In 1867 a division of the AstrsDidse was suggested in order to 

 receive the two Palaeozoic genera Seteropliyllia, M'Coy, and 

 Battershyia, Ed. & H.* I now place this division as an Alliance 

 in those Astrseidse which bud between the calicular margin and 

 the base. 



4. Subfamily Astrceidce ecBspitosce. 



{Fuj^Jiylliacecs ccespitosae, Ed. & H. (pars), and Astrceacece 

 ccespitoscB, Ed. & H., combined.) 



AstrsDidae in which the corallites are isolated in all their 

 terminal portions, being free at their sides, springing from a 

 common parent, increasing by fissiparity, separation occurring 

 rapidly or serial growth persisting. Septa entire or dentate, 

 spined or lobed. Endotheca abundant. Colonies in csespitose 

 tufts, often more or less foliaceous. Gemmation rare, but it 

 exists more frequently than has been thought hitherto. 



The insufficient morphological distinction between the Sections 

 Lithophy Iliac ees cespiteuses and the Fuphylliacees cespiteuses of 

 Milne-Edwards and Jules Haime, Hist. Nat. des Corall. vol. ii. 

 pp. 288 & 184, has been intensified by the fact that there is 

 not a very great difference between the soft structures of the 

 groups. The first section belongs to the Astrseinse, Ed. & H., 

 with spined and dentated free septal edges, and the last to the 

 Eusmilinse, with smooth septal edges. These conditions of the 

 septal edge, as already noticed, cannot be of physiological import- 

 ance, and they are found combined in the calices of species of 

 other groups of the corals. Again, the Csespitose Euphylliaceae, 

 * P. Martin Duncan, Phil. Trans. Eoy. Soc. 1867, pp. 643, 651. 



