REPORT ON CORALS — HYDROCORALLIN^E. 89 



SECTION III— GENERAL REMARKS ON THE HYDROCORALLIN.E. 



Classification of the Hydrocorallin^e. 



I place the Stylasteridse with the Milleporidse in a separate sub-order of the 

 Hydroids, which I term Hydrocorallinse in accordance with a suggestion which I made 

 in my paper On the Structure of Millepora, in the Phil. Trans., vol. elxvii. part 1, 

 1877, p. 132. The placing of the two families together seems justified in the present 

 stage of knowledge concerning them ; but the Milleporidse, in the general form of their 

 zooids, seem allied to the gymnoblastic Hydroids, whereas the presence of distinct 

 gonangia iu the Stylasteridse seems to ally these latter to the calyptoblastic group. 

 Ampullae seem certainly to be absent in the Milleporidse, 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 Hydrocorallinse and of 

 the families Milleporidse and Stylasteridse are given in the sequel in 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 Stylasteridae 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 Pourtales' 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. PAET VII. 1880.) G 12 



