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I. Family Milleporidae (L. Agassiz). 



Corallum irregular in growth, arborescent or encrusting, composed 

 of a thin superficial living layer, supported by a dead mass made up of 

 successive preceding dead layers. Pores devoid of styles, divided into 

 a series of vertically succeeding chambers by transverse calcareous 

 partitions, »tabulae«. Usually scattered irregularly, but in some species 

 grouped with tolerable regularity into systems, in which a centrally- 

 placed gastropore is surrounded by a ring of dactylopores. Nematocysts, 

 of two kinds present — the one, the three-spined form, occurring only 

 in Hydroids ; the other ovoid in shape, with a thread beset with a spiral 

 of spines. Gastrozooids short, cylindrical, with from four to six tenta- 

 cles with knob-like tips, set in a single Avhorl. Dactylozooids long, 

 filiform, and tapering, with an irregular number of short knob-bearing 

 tentacles set on at irregular intervals . Gonophores unknown, but not con- 

 tained within special cavities in the substance of the corallum, »ampullae«. 



There seems to be only one genus which can be now included in 

 the family viz, Millepora. Heliopora I have shown to be an Alcyonarian 

 (Phil. Trans. Roy. Soc, Vol. 166, pt. 1), and 1 have confirmed Prof. 

 Ver rill's results as to the nature oî Pocillopora which is Hexactinian. 

 There can be no doubt that Seriatopora is closely allied to Pocillopora. 

 There seem to be no fossil genera other than Millepora itself which can 

 with certainty be referred to the family. 



The following are the principal facts concerning the structure of 

 the Stylasteridae. 



II. Family Stylasteridae (Gray). 



Corallum arborescent, with a strong tendency to assume a flabellar 

 form, and to the development of the zooid pores on one face only of 

 the fiabellum, or on the lateral margins only 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. The gastropores usually provided with a conical 

 calcareous projection, »style«, at their bases. In some genera, a rudi- 

 mentary style present also in the dactylopores. Pores scattered irregul- 

 arly, 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 elongate cham- 

 bers, disposed radially towards 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 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, 



