LEPTOMKDUS.E — IRENOPSIS, EIRENE. 311 



marginal bulbs between every 2 tentacles. There is an excretory pore above the base ot 

 every tentacle-bulb and rudimentary tentacle. Usually 1, occasionally 2, closed lithocysts 

 between every 2 marginal-bulbs. The lithocysts are very minute and usually .contain a 

 single concretion, although occasionally there are 2 to 4 in a lithocyst. There are no mar- 

 ginal cirri. Velum narrow. There are 6 straight, slender radial-canals, 6o° apart, and a 

 simple, narrow ring-canal. The stomach is mounted upon a thick conical peduncle, the 

 mouth about at level of velar opening. Stomach very small, but it has 6 long, recurved, 

 lanceolate lips with folded edges. The 6 linear gonads are upon the outer subumbrella halves 

 of the 6 radial-canals, just above the ring-canal. Gonads, stomach, and tentacle-bulbs opaque 

 milky-yellow, other parts colorless. 



This medusa is abundant upon the surface along the coasts of the warmer parts of the 

 Indian Ocean from Zanzibar northward to the Malay Archipelago. It is best described and 

 figured by Browne, 1905. It is quite variable. In some specimens the peduncle is well 

 developed, in others it is hardly noticeable. Among 27 specimens studied by Browne from 

 the Gulf of Manaar the radial-canals ranged from 4 to II. Browne, 1905, states that his 

 " Phialidium tenue" is only an abnormal 4-rayed Irenopsis hexanemalis. 



Genus EIRENE Eschscholtz, 1829. 



Eirene, Eschscholtz, 1829, Syst. der Acalephen, p. 94. 



Geryonopsis, Forbes, 1848, British Naked-eyed Medusa;, p. 39. 



IreniumA- Irene, Haeckel, 1879, Syst. der Medusen, pp. 199, zoo. 



Irene, Bedot, 1901, Revue Suisse de Zool., tome 9, p. 483; Ibid., 1905, tome 13, p. 136 (all papers cited to 1850). 



This genus was founded by Eschscholtz, 1829, to include four species of medusae, all of 

 which had been described under other names by previous authors. Eirene viridula is the 

 oldest known species and may be taken as the type of the genus. 



GENERIC CHARACTERS. 



Eucopidae with more than 8 lithocysts and with 4 or more tentacles. There are numerous 

 small marginal cirri. The gonads are situated upon the 4 radial-canals, but they do not 

 extend over the entire lengths of the canals. The stomach is mounted upon a well-developed 

 peduncle. Hydroid undetermined. 



Haeckel, 1879, introduced the spelling "Irene" although Eschscholtz's original name is 

 Eirene. 



Eirene is closely related to Tima = (Irenium + Tima) Haeckel, but in Eirene the gonads 

 are restricted to limited parts of the lengths of the 4 radial-canals, being commonly best 

 developed upon the subumbrella and not so markedly upon the peduncle. In Tima, on the 

 other hand, the gonads extend along the entire lengths of the 4 radial-canals, over both sub- 

 umbrella and peduncle, from the bell-margin to the corners of the stomach. Eirene is chiefly 

 distinguished, however, by the absence of definite longitudinal muscle strands in its tentacles, 

 whereas in Tima a prominent band of such muscles extends down the inner (velar) side of each 

 tentacle. 



Eirene viridula Eschscholtz. 



Oceania viridula, Peron et Lesueur, 1809, Annal. du Mus. Hist. Nat. Paris, tome 14, p. 346. 



Eirene viridula, Eschscholtz, 1829, Syst. der Acalephen, p. 94.— ( ?) Bigelow, 1909, Mem. Mus. Comp. Zool. at Harvard 



College, vol. 37, p. 163, plate 36. 

 Thaumanlias cymbaloidea, Forbes, 1848, British Naked-eyed Medusa, p. 39, plate 9, figs. \a-\e=Geryonopsis delkulala, Forbes, 



Ibid., p. 39. 

 Geryonopsis forbesii, Van Beneden, 1886, Mem. Acad. Royal. Belgique, tome 36, p. 87, planche 3, figs. 1-7. 

 Tima pellucida, Schulze, 1872, Zool. Ergeb. Nordsee-Fahrt, p. 138, taf. 2, fig. 6. 

 Irene viridula, Haeckel, 1879, Syst. der Medusen. p. 202.— Maas, 1893, Ergeb. der Plankton Expedition, Bd. 2, K. c, p. 63, 



taf. 6, fign. 1, 2.— Bedot, 1901, Revue Suisse de Zool., tome 9, p. 483; Ibid., 1905, tome 13, p. 136 (literature cited to 1850). 

 Irene mollis, Torrey, 1909. University California Publication, Zool., vol. 6, p. 26, fig. 11. 



Bell very flat, 25 to 50 mm. wide and about 6 to 15 mm. high. Gelatinous substance thin 

 and of great tenuity. 50 to 60 tentacles not more than a fifth as long as the bell-radius, and 

 about 100 even smaller tentacles not more than half as long as the longer tentacles. All the 

 tentacles have wide, conical, basal bulbs which taper rapidly into the thread-like lash of the 

 tentacle. The 100 smaller tentacles are each flanked by a pair of coiled lateral cirri, but 



