Part II. — Stichodactylince and Zoanthece. 137 



coloured from all the rest. They are all, however, on the same radii as the inner 

 rows, which are not cyclic. 



In Actinoporus the tentacles are simple or lobed vesicles, are practically all 

 alike, and occupy all the radial divisions, two or more irregular rows com- 

 municating with the same mesenterial chamber. 



Where the tentacles are so crowded, some of these relationships and 

 distinctions are not easily recognized in contracted, preserved specimens. In 

 living polyps, they can more readily be made out, often facilitated by colour 

 distinctions. 



I think it is desirable to have some division expressive of the similarity, or 

 otherwise, of the tentacles in any genus, and therefore propose the following 

 Sub- orders : — 



Heterodactylisle. 



Stichodactylinse, in which the tentacles are of two forms, usually marginal 

 and accessory, and separated by a naked portion of the disc. Examples — Phy- 

 manthus, Actinotryx, Rhodactis, Cryptodendron, Heterodactyla. 



HOMODACTYLIN.E. 



Stichodactylinse, in which the tentacles are all of one kind, simple or complex, 

 and usually follow one another in continuous rows. Examples — Discosoma, 

 Ricordea, Stoichactis, Radianthus, Corynactis, Homostichanthus, Actinoporus. 



Generally the more central tentacles are smaller or less complex than the 

 more peripheral, but within the same species they are all formed on one plan. 



Dr. Carlgren (1891, 1893) has erected the tribe Protantheae, of which the most 

 salient character is that the column-wall and stomodasmn possess an ectodermal 

 ganglion and longitudinal muscle layer. First formed to include the genera 

 Gonactinia and Protanthea, in his later paper he embraces Thaumactis 

 medusoides, Fowler, and the genera Corynactis and Corallimorphus, re- 

 presenting the families Thaumactinidae and Corallimorphidse respectively. 

 Thaumactis has since been shown by Professor Haddon and myself (1896, 

 p. 158) to be included in the family Aliciidse, and I do not consider the presence 

 of an ectodermal musculature of sufficient importance to warrant the separation 

 of the Coralliinorphidse from its more natural place among the Stichodactylinse. 



A columnar and stomodseal ectodermal musculature and nerve layer are now 

 known for many Hexactinise, the other characters of which indicate that they belong 

 to totally different families. Professor M c Murrich (1893, p. 143) refers to the 

 probable occurrence of an ectodermal musculature in Halcurias pilatus ; I have 

 recorded it (1897) in two species of Bunodeopsis, and describe its presence in 



