32 McMURRICH. (Vou. III. 
Eumenides ophiseocoma described by Lesson (28) for New 
Guinea may, perhaps, be distantly related to the forms referred 
to this sub-tribe, but differs in so many points that it cannot be 
included with them. 
Hertwig associated Ophzodiscus with the Paractinidz, which 
belong to the sub-tribe Actininz as defined in this memoir, on 
account of the circular muscle being imbedded in the mesogleea, 
at the same time holding open the question as to the propriety 
of erecting the genus into a special family. Since the various 
sub-tribes are characterized by the nature of the tentacles, and 
since the possession of the peculiar pseudo-tentacles, to employ 
the name Hertwig has applied to them, is so characteristic, I 
have thought it well to establish for the two genera, not merely 
a new family, but a new sub-tribe, making the division which 
they constitute of equal importance to the Stichodactyline or 
Thalassianthine, This sub-tribe is probably more nearly allied 
to the Actininz than to the other sub-tribes of the Hexactinia, 
since the tentacles are arranged in cycles and not radially, and 
are simple and conical. Their situation on the margin is an 
important point, however, which in addition to the possession 
of pseudo-tentacles distinguishes the sub-tribe from that of the 
Actininz, and associates it, to a certain extent, with the Sticho- 
dactylinz, in many of which the simple tentacles are marginal 
in position. Duchassaing and Michelotti considered the genus 
Lebrunea to be close to Phyllactis, but such an alliance is 
unquestionably erroneous. The pseudo-tentacles have no rela- 
tionship either in position or structure to the fronds of the 
Phyllactidz. 
The separation of the two genera, Lebrunea and Ophiodiscus, 
in distinct families will probably be found necessary eventually, 
inasmuch as the differences between them, such as the presence 
in one and the absence in the other of a circular muscle, and 
the specialization of the mesenteries into muscular and gono- 
phoric cycles in Ophzodiscus, are probably of more than generic 
importance. But until a greater number of forms belonging 
to the group have been discovered, and their structure thor- 
oughly studied, the establishment of separate families seems 
unnecessary. 
