432 Happon—The Actiniaria of Torres Straits. 
endodermal muscle are long, very numerous, and often branched. The complex 
character of these plaitings is most marked round the origin of each sucker, 
so that practically a local, circumscribed, endodermal sphincter muscle is formed 
(Pl. xxvut., fig. 4). 
The mesenteries are arranged in the ordinary Hexactinian plan, and consist of 
24 pairs (6 +64 12), of which two are directives. They are all fertile. The 
retractor muscles are large, and consist of a number of simple or but slightly 
complex plaits (Pl. xxvit., fig. 5); a strong pennon muscle is present. 
The endodermal sphincter is of a form intermediate between the diffuse and the 
circumscribed types; it might, perhaps, be termed ‘“ restricted,” whereas the 
typical circumscribed muscle is ‘ constricted.” Its character is best understood 
by the figure (Pl. xxvmt., fig. 4). It is small for the size of the polyp; the most 
distal plaits are arranged so as to form a dendritic group. 
MYONANTHUS, M'M., 1893, p. 151. 
Actiniidee with smooth column ; no acrorhagi; aggregated endodermal sphincter 
muscle. 
I have compiled a definition of M‘Murrich’s new genus from the description 
he has published of a new form which is mainly characterised by possessing a 
peculiar kind of sphincter, which appears to be a diffuse type which is in process of 
becoming mesoglozal ; for this variety he proposes the name ‘‘ aggregated.” There 
are several cases known where the first steps, so to speak, in this process have been 
taken (e.g. Diplactis Bermudensis, M°M., Proc. Acad. Nat. Sci. Phila., 1889, 
p- 111), and also in the genus Parazoanthus, but in this genus the process has gone 
a step further. 
M*Murrich points out that “this form is not readily referable to any of the 
recognised families. On the whole, however, it seems to approach more nearly to 
the Antheade than to any of the others” (p. 153). 
M. ambiguus, M°M. 1893, p. 161. 
ANTHEOMORPHE, Hertw., 1882, p. 30. 
Actiniidze with smooth column; capitular margin not forming a collar, and 
without acrorhagi ; tentacles long, in a single row ; no sphincter muscle ; gonads on 
all the mesenteries. 
[ agree with M*Murrich (1893, p. 134) in placing the Antheomorphide of 
Hertwig, “for the present, with the Antheade” (Actiniidz), 
A, elegans, Hert., 1882, p. 30. 
