1867.] r)R. J. E. GRVY ON zoanthin.t;. 233 316. SiPHONARIA ATRA. Siphonaria atra, Quoy et Gaim. Voy. de I'Astrol. vol. ii. p. 337, pi. 2;). f. 41, 42. Painted inside with broad black stripes. Found also in Japan and the Pacific Islands. Length 1 inch. 5. Notes on Zoanthina, with the Descriptions of some New Genera. By Dr. J. E. Gray, F.R.S. IVI. Milne-Edwards, in his ' Coralliaires ' (vol. i. p. 226), divides the Actinidce into two groups: — one in which the covering of the body remains soft and does not form a polyperoid ; and, secondly, the Zoanthince, in which the integument of the body thickens and is strengthened with sclerotes, so as to form a coriaceous polyperoid. But in the larger character of the family (at p. 298) he adds that they are aggregate polypes, which multiply by basal buds formed of the tegumental tissues ; and he confines the family to the genera Zoanthus and PaJythoa, — the first arising from root-like stolons, and the other from a broad laminal expansion. There can be no doubt that the grou}) so defined is very natural ; but there are several genera of Actinince that have considerable re-lation to Zoanthus, not mentioned by Milne-Edwards, which do not come under either of these characters : that is to say, there are some which have the outer skin thick and strengthened with imbedded sand or calcareous particles, which are not aggregate and do not increase by basal buds, arising from neither root-like fibres nor an ex-panded base, but which are free ; on the other hand, there are other genera which do not arise from basal buds, some of which have a thick cartilaginous skin not strengtlieued by sand or calcareous con-cretions, and others which have a thin membranaceous skin. x\ll these genera have only a single or double row of very short tentacles, which are placed round the edge of the oral disk far from the mouth, which when the oral disk is contracted are completely hidden. I think that these animals should form a family distinct from Aciinidee, which may be called Zoanthidee. The zoanthoid polypes, in Lesueur, Dana, and Milne-Edwards's * Coralliaires,' are divided into groups, according to the form of the base from which they arise, — some, as the Zotuithi, having cylindri-cal stolons, and others, as the Palythoa, an expanded foliaceous base ; the latter are again divided according to whether the polypes are entirely or partially separate, or confluent nearly to the mouth of the cells, — all, no doubt, very good characters for the separation of the species into groups. They separate themselves into two very natural groups, according to the structure of the external surfaces of the polypes. In many, which may be called Zoanthi malacodermi, or soft-
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