MEDUS. 17 
definition, and instead of saying ‘“‘ numerous” centripetal canals, to fix the number at 
four or more. 
The type species of the genus Sibogita is S. geometrica, Maas. This Medusa, 
according to Maas’ figure, certainly has the appearance of possessing radial canals with 
lateral branches, as stated by Maas, and there is no indication of the lateral branches 
being really centripetal canals, which originate from the circular canal and afterwards 
join the radial canals. 
It was my intention to place the Antarctic species in a new genus, but Mr. 
Bigelow’s account of the development of the canal system of Sibogita simulans has led 
me to place the new species in the genus Sibogita. I believe that Mr. Bigelow is right 
in associating his two new species with the genus Svbogita, especially as the tentacles 
and the umbrella are similar to those of the type species. 
The two specimens of Sibogita simulans collected in the tropical Pacific have eight 
adradial blind centripetal canals, but the single specimen from the Behring Sea is older 
than those two and has twelve centripetal canals, which all unite with the base of the 
stomach. In S. nawarchus the centripetal canals are more numerous and are all blind. 
Sibogita borchgrevinki has only four centripetal canals, which may or may not unite by 
lateral branches with the base of the stomach. 
In the species described by Dr. Maas and by Mr. Bigelow the gonads are 
transversely folded, and occupy the whole space between the perradii. The gonads of 
the new Antarctic species are distinctly peculiar, as they are in pockets, and the whole 
stomach is converted into a reproductive organ. 
SIBOGITA BORCHGREVINKI. 
(Plate II., figs. 1-5.) 
Description of the Species—Umbrella ovoid, a little higher than broad, and very 
thick. Velum narrow. Stomach about one-third the length of the umbrellar cavity, 
somewhat conical, tapering slightly towards the mouth, and with four perradial ridges. 
Mouth with four small lips and the margin slightly folded. Four perradial canals, 
and four interradial centripetal canals. The latter may or may not unite with 
the cruciform base of the stomach. Gonads (male) in pockets and embedded in 
the wall of the stomach, with definite openings to the exterior. About sixteen 
fairly long, hollow, smooth tentacles, each with a large terminal bulb containing 
nematocysts. 
Size—Umbrella 15-18 mm. in width and 20 mm. in height. 
Three specimens of this interesting Medusa were taken at the surface during 
November 1899 at Cape Adare by the ‘ Southern Cross’ Expedition. The specimens 
are in very good condition, but all have the margin of the umbrella so very much 
contracted that it was necessary for examination to cut it into pieces. Two of the 
specimens are fully ripe males, and the third specimen has shed its gonads. 
