Happon—The Actiniaria of Torres Straits. 411 
Dr. Fowler (Quart. Jour. Mier. Sci. xxix., 1889, p. 143) described a new form 
which he called Thaumactis medusoides. Owing to the extreme retraction of his 
specimen, and other causes, Dr. Fowler was misled concerning it, and thought it 
was a new type of Actiniarian; Mr. Duerden and I, however, showed that, save 
for the ectodermal muscle fibres in the capitulum and cesophagus, this form was 
evidently allied to Alicia and Cystiactis, and therefore belonged to the Aliciide. 
While acknowledging with Carlgren the phylogenetic importance of the 
presence of ectodermal muscle fibres in the body-wall of certain sea-anemones, L 
do not think we are at present justified in making this the sole diagnostic 
character of a prime group of the Actiniaria. On the whole, I am more inclined 
to lay stress on the arrangement of the mesenteries, and the nature and position 
of the tentacles, although, on the other hand, either of these characters cannot 
be always implicitly relied upon. 
Perhaps all the Protactinie (Protanthex) have ectodermal muscles; but, 
according to my position, certain forms belonging to other groups may also 
possess them, in which case it will probably be found that these are the lowest, 
ae. the least specialised members of those several groups. 
We must face the difficulty in a systematic study of the Actiniaria, as in other 
classifications, of allied forms which refuse to be comprised within a diagnosis 
that will comprise these alone, owing to the fact that some of them possess 
characters which others do not, and which ally them to another group or even to 
diverse groups. 
Unfortunately M*Murrich and Carlgren synchronously proposed their several 
names for this tribe, so that it is difficult to determine which has the priority. 
Putting aside the precise date of publication I am inclined, for the above men- 
tioned reasons, to adopt M‘Murrich’s name. 
Family.—Gonacrinup#., Carlgren, 1893. 
Gonactinia, . . M. Sars, 1851 (cf. Carlgren, 1893, p. 31). 
Oractis,. . . . M*Murrich, 1891, p. 135 (cf. 1893, p. 138). 
Protanthea, . . Carlgren, 1891, p. 81 (cf. 1893, p. 24). 
? Seytophorus, . . Hertwig, 1882, p. 104 (cf. M*Murrich, 1891, p. 134; 
1893, p. 140). 
? Haleurias,. . . M*Murrich, 1898, p. 142 (cf. Carlgren, 1893, p. 136). 
Tribe V.—HEXACTINIA, R. Hertwig, 1882. 
Actiniaria, with usually six, but there may be eight or ten, pairs of perfect 
mesenteries which form the primary cycle, and to which may be added a varying 
number of additional cycles, perfect or imperfect, the mesenteries of which develop 
: 3 P2 
