Happon—The Actiniaria of Torres Straits, 489 
1897), he suggests that Megalactis might be placed among the Acremodactylide, a 
family which he thus describes :—‘‘ Actinians with a pedal disk; smooth (or also 
warty P), body-wall, without a rim. No cinclides. Tentacles with simple or 
agglomerated branched evaginations, marginal, the inner larger than the outer. 
Sphincter absent. Mesenteries not very numerous. No acontia.” In the absence 
of illustrations it is not very easy to understand this new family. As he gives as 
a synonym ‘ Heteractidze (pars)? Andres, 1883,” it is evident that he, with 
M°Murrich, regards this family as one of the Actinine, in which the tentacles are 
more or less branched. For the present I still regard these forms as members of 
the Stichodactylinze, and I am inclined to regard the “tentacles” as tentacular 
prolongations of the disk, analogous to those of Actineria and Thalassianthus, 
which bear small complex tentacles rather than tentacles proper, which are 
provided with branches. 
Instead of introducing a new term into Actiniarian nomenclature, I take the 
name of the most important genus for the designation of the family. Probably 
Megalactis, and perhaps Acremodactyla, belong here. 
Actinodendron. ? Acremodactyla. 
Megalactis. ? Actinostephanus. 
ACTINODENDRON, Blainy. 
AcTINODENDRON, Blainyille, 1830, p. 287, 1834, p. 320; Milne-Edwards, 1857, 
p. 295; Andres, 1883, p. 303. Acrinra, pars, Quoy et Gaim., 
1833. 
Actinodendridz with a smooth body; the oral disk is not expanded, but its 
margin is produced into forty-eight elongated non-retractile lobes, on which are 
situated the branched tentacles. Sphincter muscle absent(?). Twenty-four pairs 
of mesenteries in three cycles. All the mesenteries, except the directives, are 
fertile. 
The earlier definitions of this genus refer only to external characters, as no 
anatomical investigation has previously been made of any of its species. I have 
not been able to discover a sphincter muscle, and it is very probable that it is 
altogether absent. All the specimens examined had the typical Hexactinian 
arrangement of the mesenteries; the retractor muscle of all the mesenteries is 
very strong, and consists of a broad band of closely set, relatively simple plaits 
The first two cycles (6 + 6) are perfect, and there is a pair of directives. The 
third cycle consists of twelve pairs of small, but by no means ill-developed 
mesenteries. All the mesenteries are fertile, with the exception of the directives. 
TRANS. ROY. DUB. S0C., N.S. » VOL. VI., PART XVI. 4B 
