ANTHOMEDUS.E STEENSTIU'I'IA, HYBOCODON. 37 



In most specimens there is a blindly-ending axial canal extending into the gelatinous substance 

 of the apical projection, but this is not constantly present. The gonads are developed upon 

 the sides of the stomach, leaving only the basal and mouth ends of the manubrium free. A 

 cross-section shows that they are separated by 4 minute, perradial, longitudinal lines. There 

 are therefore 4 interradial gonads. There are no medusa-buds produced by the medusa. 



The entoderm of the manubrium, radial-canals, and tentacle-bulbs is filled with yellow 

 pigment granules. The nematocyst clusters on all 4 tentacles are red. 



Found quite commonly in the Malay Archipelago, at Sulu, Ternate, Damar, Manifa, 

 Saleyer, and Amboina. 



This form differs from the closely allied S. letrabrachia Bigelow, from the Maldive 

 Islands, in that in the Maldive species there are a few rings of nematocysts upon the ten- 

 tacles, whereas in S. bigelou'i there are only warts, not inclosed rings. Also there appears to 

 be no axial canal in S. tetrabrachia, whereas this is usually seen in 5. bigelowt. The size 

 constitutes a disparity in the two medusae 4 mm. high in S. tetrabrachia and about 13 mm. in 

 S. bi^elowi. Future studies will probably show that these distinctions are not of specific 

 value, but merely changes due to growth and variation, and that the two medusae are identical 

 and should be called S. tetrabrachia. "Euphysa" tentaculata, Linko, 1905 (Zool. Anzeiger, 

 Bd. 28, p. 214), from Barents Sea has also 3 well-developed tentacles, and is 5 mm. high, 

 with orange-colored manubrium and oval bell. It may be Hybocodon pcndula. 



Steenstrupia australis. 

 Euphysa ausiralis, VON LENDENFELD, 1884, Proc. Linnean Soc. New South Wales, vol. 9, p. 586, plate 21, fig. 33. 



Bell is 2.5 mm. high, 1.7 mm. wide. Half-egg-shaped and symmetrical. No lines of 

 nematocysts over the exumbrella. One very long retractile tentacle, 2 to 3 times as long as 

 the bell-height. This tentacle has a large basal bulb, and is covered with rings of nemato- 

 cysts. The other 3 tentacles are mere basal bulbs terminating in a knob-shaped cluster of 

 nematocysts. Velum well developed. 4 straight radial-canals. Manubrium arises from the 

 center of the umbrella cavity, and is cylindrical and about half as long as the bell-height. 

 The gonad encircles the manubrium. Mouth deep violet. 4 brown patches upon the gonad, 

 and a few brown spots on manubrium near its base. Tentacle-bulbs and the large tentacle 

 brown with violet spots. Port Jackson, New South Wales, in May and June. Rare. 



Hydroid unknown. 



Genus HYBOCODON L. Agassir, 1862. 



Htbocodon, AGASSIZ, L., i86z, Cont. Nat. Hist. U. S., vol. 4, p. 243. AGASSIZ, A., 1 865, North Amcr. Acal., p. 193. VANHOFFEN, 

 1891, Zool. Anzeiger, Bd. 14, p. 443. BROWNE, 1896, Proc. Zool. Soc. London, p. 466. HARTLAI B, 1905, Zoolog. Jahr- 

 buchern, Suppl. 6, p. 544; 1907, Nordisches Plankton, Nr. 12, p. 96. 



HybocoJon + ArnphicoJon, HAECKF.L, 1879, Syst. der Medusen, pp. 33, 35. 



Amphirodon, BROWNE, 1901, Annals and Mag. Nat. Hist., ser. 7, vol. 9, p. 275. 



Diplura, ALLMAN, 1871, Monog. Tubularian Hydroids, p. 326. 



Corymorpha, AGASSIZ, A., 1865, /feiW., p. 192. 



This genus was established in 1862 by L. Agassiz for Hybocodon prohfer, a medusa 

 which arises by budding from a Corymor^/ja-like hydroid on the New England coast. Accord- 

 ing to Browne, 1896, this medusa is also found off the northern coast of Europe. It is prob- 

 able that the same medusa was described by Steenstrup, 1842, from Iceland, as Corymorpha 

 fritillaria, but the hydroid from which Steenstrup supposed this medusa to be derived is 

 certainly not HvbocoJon, but may be an Arnalthira or Diplura. Steenstrup does not figure 

 a basal circlet of tentacles upon the polypites, which have only an oral circlet, and below 

 this a circlet of medusiform gonophores, each with a 4-sided bell, and 4 equally developed 

 rudimentary tentacles. It is probable that the hydroids of Hybocodon differ more among 

 themselves than do the medusae, and no final classification of the medusae can be attempted 

 until all of the hydroids have been discovered. 



GENERIC CHARACTERS. 



Codonidae with asymmetrical bell. One of the 4 radial-canals is long. I short, and 2 of 

 medium length. There are I or more long tentacles at the foot of the long radial-canal; 

 and 3 small or rudimentary tentacles, I at the foot of each of the 3 other radial-canals. The 

 hydroid is HybocoJon. 



