36 EDWARD T. BROWNE. 



TRACHOMEDUS.E. 



FAMILY TRACHYNEMID^. 



Genus PANTACHOGON, Maas, 1893. 



Generic Characters. Trachynemidse with numerous similar tentacles ; with 

 gonads extending along the radial canals, and separated from the stomach by a 

 short interval. 



PANTACHOGON SCOTTI. 

 (Plate III., figs. 5 and 6.) 



Description of the Species. Umbrella hemispherical, a little broader than high, 

 and fairly thin. Velum very broad. Stomach very small, roundish, and not on a 

 peduncle. Mouth with four short lips. Eight very narrow radial canals. Gonads 

 long, extending over the proximal two-thirds of all the radial canals, and separated 

 by a short interval from the stomach. Tentacles all alike, very short and numerous, 

 about fifteen in each octant. 



Size. Umbrella up to about 4 mm. in diameter. 



The ' Discovery ' collection contains twenty-five specimens of this little Medusa. 

 They were all taken from under the ice in McMurdo Sound from May to December. 



It was not until after much consideration that I decided to place this new species, 

 which is named in honour of the leader of the ' Discovery ' Expedition, in the genus 

 Pantachogon. The type species of the genus is Pantachogon haeckeli, Maas (1893), 

 which has gonads distributed at intervals along the whole length of the radial canals. 

 Another species is P. ruhrum, Vanhoffen (1902), which has gonads upon the outer 

 half of the radial canals. The new species has its gonads upon the proximal part 

 of the canals, where they form a continuous band. There is a difference in the 

 structure of the gonads compared with the type species, but I am rather inclined to 

 regard this difference as a specific character. I think it is best to leave the new 

 species in the genus Pantachogon until better specimens have been examined and the 

 sense organs found. 



The shape of the umbrella in most of the specimens is somewhat plano-convex, 

 and, I believe, the shape is due partly to the shrinkage of the jelly and partly to the 

 curling inwards of the margin of the umbrella. The drawing of fig. 5 is based" upon 

 a single specimen which is in fairly good condition. 



Some of the specimens show a saucer-shaped depression at the apex of the 

 umbrella, just over the top of the stomach. I am not sure whether the depression 

 is a natural one or the result of shrinkage. There appears, however, to be a decrease 

 in the thickness of the jelly above the stomach. Several specimens have a ring-shaped 

 stomach, and the shape is due to the contracting back of the wall of the stomach. The 



