.MHDUS^E. 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 Sibogita, 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. nauarchus 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. 

 Moutli vvith 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 

 uematocysts. 



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. 



