12 EDWARD T. BROWNE. 
This thick base is apparently absent in Jf australis, but as the top of the umbrella is 
crushed in, it is impossible to see every detail clearly. 
The arrangement of the tentacles is similar in both species. There are two 
tentacles, one placed behind the other (PI. IV., fig. 7), on each of the four perradial 
bulbs. My figures of MM hartlaubi show the tentacles in this position, but I omitted 
to direct attention to the arrangement of the tentacles in the description of the 
species. Both species have practically the same kind of basal bulb. The tentacles 
of M. australis are closely contracted, and it is impossible to make out the arrange- 
ment of the nematocysts upon the tentacles. This is unfortunate, because if the 
structure of the tentacles should differ from M. hartlaubi, we should have a useful aid 
towards the determination of the species. I have decided to give the Antarctic 
Margelopsis a specific name because I cannot prove that it is identical with 
M. hartlaubi. One really wants another specimen in far better condition than this 
to definitely elucidate the specific characters. 
The Meduse which Prof. Dendy (1902) found attached to the Hydroid Pela- 
gohydra mirabilis, which was washed up on the coast of New Zealand, probably 
belong to the medusoid genus Margelopsis. As these Meduse had not detached 
themselves from the Hydroid and were without gonads, they must be regarded as 
quite early stages. They have five tentacles on each of the four perradial basal 
bulbs. These tentacles are arranged in two pairs, one behind the other, with the 
fifth tentacle by itself on the innermost side of the basal bulb. 
Famity TIARIDA. 
CatTaBLEMA, Haeckel, 1879. 
Generic Character.—Tiaride with radial canals having lateral branches or 
diverticula. . 
The above definition of the genus may be regarded as rather vague, but it can 
be added to when all the genera and species of the Tiaride have undergone a 
thorough revision. The conformation of the sexual organs has hitherto been used 
as the chief means of distinguishing the different genera, but I am rather inclined 
to use the shape of the gonads for one of the specific characters. A new Antarctic 
species compels me either to omit the gonads from the generic character or to 
establish a new genus. I prefer, at any rate for the present, to place the new 
species in the genus Catablema. The new species is named after the late W. F. R. 
Weldon, who was for some years Professor of Zoology in University College, and 
who gave me my first lessons in this fascinating subject. 
One of the characters which has always been associated with the genus Catablema 
is the presence of diverticula on the radial canals; but other species with similar 
diverticula have been placed in the genus Turris, because the conformation of their 
gonads is not like that in the typical Cutablema. The type species of the genus Turris 
