158 EXPEDITION OF THE "ALBATROSS," 1899-1900. 



Pelagia tahitiana, sp. nov. 

 Plate 8, Jigs. 34, 35. 



Immature individual. The disk is twice as broad as it is high, and is 

 about 16 mm. in diameter. The ex-umbrella is quite regularly sprinkled 

 over with large wart-like papillae which bear nettling cells. The papillae 

 near the aboral apex of the disk are larger than the others, those near 

 the bell-margin being very small. There are eight hollow tentacles, the 

 distal three-quarters of which are covered profusely with nettling cells. 

 These tentacles are each about three-quarters as long as the bell-diameter. 

 Eight marginal sense organs alternate with the tentacles. Each sense 

 organ contains a mass of dark-red pigment of entodermal formation. 

 There are sixteen partially cleft lappets. The mouth is surrounded by 

 four well developed crenulated palps which are about three-quarters as 

 long as the bell-diameter. There are four inter-radial gonads, each one 

 of which is horseshoe shaped, with its concave side turned outward 

 (centripetally). Each gonad is furnished with from eight to twelve 

 short gastric cirri and a well developed sub-genital pit. The stomach is 

 a wide lenticular space at the centre of the disk. It gives rise to sixteen 

 radial pockets which extend outward, eight to the tentacles and eight to the 

 sense organs. These pockets are entirely separated each from each, and there 

 is no ring canal. There is a well developed set of circular muscles in the 

 sub-umbrella, and also a powerful radial set of sixteen muscle strands which 

 alternate in position with the tentacles and sense organs, and extend down 

 the septaa between the radial pockets. In addition to these there are sixteen 

 radial muscle strands in the ex-umbrella. These extend to the bases of the 

 tentacles and sense organs. The disk and palps are of a dull amber-yellow 

 color and the tentacles are of a darker hue. The nematocyst cells over the 

 ex-umbrella and the palps are orange-red, and the genital organs are of a 

 dull ochre color. A single specimen of this medusa was found on the sur- 

 face south of Rangiroa Island, Paumotus. 



S" ; September 24, 1899 ; off Rangiroa, Paumotus Islands. 



