REPORT ON CORALS — HYDROCORALLIN^. 93 



1. Millepora, Linnaeus (Syst. Nat., ed. 10, t. i. p. 790, 1858). 

 Genus with the characters of the family. 



2. Family Stylasterid.e, Gray. 



Ccenosteum arborescent, with a strong tendency to assume a flabellar form, and to the 

 development of the zooid pores on one face only of the flabellum, or on the lateral 

 margins of the branches composing it. In some genera a superficial layer only of 

 the coral is living ; in others, nearly the entire mass retains its vitality. Pores 

 with tabulae in two genera only. Gastropores usually provided with a conical 

 calcareous projection, " style," at their bases. In some genera a rudimentary style 

 present in the dactylopores. Pores scattered irregularly, or grouped into more or 

 less symmetrical systems, composed of a centrally-placed gastropore surrounded by 

 a circlet of dactylopores. In some genera the mouths of the dactylopores appear as 

 elongated chambers, disposed radially round the centre of the gastropore into which 

 they open, and the chambers being separated from one another only by thin partitions, 

 " pseudosepta " ; the systems, " cyclo-systems," simulate closely the calicles of Hexactinian 

 corals. Nematocysts of two kinds, large and small, and of uniform shape in all the 

 genera. Three-spined nematocysts absent. Gastrozooids cylindrical or flask-shaped 

 in form, always entirely retracted within the gastropores when at rest ; those of the 

 former shape with from four to twelve tentacles, set in one whorl, and regular in 

 number in all the gastrozooids in each species ; those of the latter devoid of tentacles. 

 Dactylozooids simple elongate- conical bodies, devoid of tentacles., sometimes capable 

 of entire retraction within the pores, sometimes not. Stocks of distinct sexes. Gono- 

 phores adelocodonic, developed within sacs, " gonangia," which are contained within 

 special cavities in the substance of the ccenosteum, <: ampullar." Stocks of the two sexes 

 alike in form as far as known, except in the size of the ampulla?, which are larger and 

 more prominent in the females. Ampullae containing in male stocks several gono- 

 phores ; in female, in some genera, a single gonophore, in others several. Spadix, in 

 the female gonophores, cup-shaped, embracing a single ovum only, which becomes 

 developed into a planula within the gonangium. 



1. Sporadopora, Moseley (Phil. Trans. Roy. Soc, 1878, part 2, p. A74) = Polypora, 

 Moseley (Proc. Roy. Soc, No. 172, 1876, pp. 94, 95). 



Ccenosteum pure white, composed of finely reticular but compact ccenenchyrn, forming 

 stout vertical stems, usually compressed from before backwards, so as to be oval in trans- 

 verse section. Stem giving off a limited number of irregularly dichotomous branches, 

 which are flattened like it, and tend to coalesce by their lateral margins and assume a 

 flabellate form, which is sometimes somewhat curved. Surface of the ccenosteum 



