102) 
eo) 
REPORT ON CORALS—HYDROCORALLIN 8. 
SECTION IIL.—GENERAL REMARKS ON THE HYDROCORALLIN&. 
CLASSIFICATION OF THE HyDROCORALLIN A. 
I place the Stylasteride with the Milleporide in a separate sub-order of the 
Hydroids, which I term Hydrocorallinee in accordance with a suggestion which I made 
in my paper On the Structure of Millepora, in the Phil. Trans., vol. clxvi. part 1, 
1877, p. 132. The placing of the two families together seems justified in the present 
stage of knowledge concerning them ; but the Milleporide, in the general form of their 
zooids, seem allied to the gymnoblastic Hydroids, whereas the presence of distinct 
gonangia in the Stylasteride seems to ally these latter to the calyptoblastic group. 
Ampulle seem certainly to be absent in the Milleporide, and their gonophores are, there- 
fore, probably developed free of the ccenosteum. Further research may lead to the 
separation of the two families. The characters of the sub-order Hydrocorallinee and of 
the families Milleporidee and Stylasteride are given in the sequel im a concise tabular 
form, and also in a series of more extended and comprehensive statements in which no 
known detail of importance is omitted. 
The components of the family Stylasteridee have hitherto been classified from a 
knowledge of the structure of the ccenosteum alone, and even this has been but imper- 
fectly investigated in most instances ; further, the descriptions given of the genera and 
species have been distorted by the violent efforts made by naturalists to discover septa 
and interseptal chambers in the so-called calicles of these supposed anthozoan corals. 
The descriptions of the genera at least, thus required to be rewritten, and modified 
according to the present knowledge of the structure of the members of the family. 
This has been attempted in the sequel, where the characters of the genera given 
embrace those derived from the structures of the soft tissues as well as of the hard. 
Unfortunately the soft structures are known in only one species in almost all the 
genera, and in almost all in but one sex. Hence the classification here given will 
doubtless need subsequent modification. It merely professes to be an attempt to 
define the genera in the best manner now possible. 
In the case of three genera, Labiopora, Stenohelia, and Conopora, nothing is known 
of the soft structures. 
Count de Pourtalés’ genus Lepidopora is here emerged in Errina, from which it 
can hardly be considered distinct. The lid-like coverings of the gastropores, by the 
presence of which the genus Lepidopora is distinguished, are most frequently composed 
of fused dactylopore projections, and do not in most instances consist of special eleva- 
tions of the margins of the gastropore mouths themselves, although this latter is some- 
times the case. Errina labiata, a species of which the structure is described in the 
present treatise, seems to form a gradation between the species described as belonging to 
(ZOOL. CHALL., EXP.—PART vil.—1880.) G12 
