12 EDWARD T. BROWNE. 



This thick base is apparently absent in M. 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 M. 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 Medusae 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 Medusae 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. 



FAMILY TIARID^. 

 CATABLEMA, Haeckel, 1879. 



Generic Character. Tiaridse 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 Tiaridse 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. E. 

 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 Tunis, because the conformation of their 

 gonads is not like that in the typical Catablema. The type species of the genus Tun-is 



