36 EDWARD T. BROWNE. 
TRACHOMEDUSA. 
Famity TRACHYNEMIDA. 
Genus PantacHocon, Maas, 1893. 
Generic Characters.—Trachynemide 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 (1898), 
which has gonads distributed at intervals along the whole length of the radial canals. 
Another species is P. rubrum, Vanhéffen (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 
