\ vrin IM Knrs.K- -ST< >M< >rt ><-.\. Ill 



margin. These lack ocelli. The 4 radial-canals are wide and flat. The boundaries of the 

 radial-canals and of the ling-canal are often bluntly serrated. The manuhrium is flask- 

 shaped; there is no peduncle and the 4 lips are cruciform, crenulated, and curve slightly 

 upward. The ectoderm of the upper part of the manuhrium on both sides of the 4 ladial- 

 canals is thrown into interradial folds or convolutions and the gonads are developed in 

 this region. 



In the male the color of the manuhrium varies from intense green to translucent ocher- 

 yellow or cream-color. The basal bulbs of the tentacles in the male vary from faint to deep 

 purple. In the female the manubrium is usually translucent ocher-\ t -\\n\\ or cream-colored, 

 but occasionally straw-colored or faintly green. The tentacle-bulbs of the female are usualU 

 translucent milky or ocher, but occasionally one is found having faintly purple tentacle-bulbs. 

 These sexually dimorphic color peculiarities are seen in the smallest and youngest medusae 

 as well as in adults. In very young medusae the apical projection is small or absent. There are 

 2 tentacles and only 2 rudimentary tentacle-bulbs. 



This medusa is common at Newport, Rhode Island, from |ulv 15 to September. It is 

 not common at Tortugas, Florida, and is not seen north of Cape Cod, Massachusetts. On 

 October 28, 1907, I found two male medusae of this species oft" Mousehole, Mounts Bay, 

 Cornwall, England. 



This species furnishes that which is probably the most remarkable instance of sexual 

 dichromatism to be met with among the hydromedusae, the color differences affecting parts 

 other than the gonads. 



The two males found off the coast of Cornwall, Kngland, were each 2.2 mm. high and 

 similar in all respects to the typical American form; with intense green manuhrium and 

 purple tentacle-bulbs, without ocelli. The bell-apex was solid and gelatinous. 1 believe that 

 S. apicata of America. IS identical with S. Jlni'inn of Europe. The European medusa may 

 have more rudimentary tentacle-bulbs, hut these are very variable in number in the Ameri- 

 can form. 



Stomotoca atra Agassiz. 



Stottiotora atrn, AGASSI/, I... i862 f Cont. Nat. Hist. U. S. f vol. 4, p. 347.- A<.-\SM/, A., iM>^. N^rth AIIMT. \<,il., p. it>^, figs. 

 271-27;. H^H-KH., 1X71), Sysl. ilcr Meilusen, p. 53. 



Bell 20 to 25 mm. high, 20 to 22 mm. wide. Bell-shaped, higher than a hemisphere. 

 2 long, highly contractile tentacles, and about 80 small rudimentary tentacle-bulbs. Stomach 

 about half as long as the depth of the bell-cavity. Swollen, 4-sided, and mounted upon a 

 peduncle. 4 lips. The gonads a re 8 ad radial, linear cross-foldings upon the sides of the Stomach, 

 each gonad consisting of I 2 to 15 folds as in Turns. The mouth is dull yellow. Gonads dark- 

 brown to almost black. Tentacles light-brown. 



Found by A. Agassiz in great numbers in Port Townsend, Washington, Pacific coast of 

 the United States; from |une until September. 



Stomotoca octaedra. 

 Plate 1 1, ti);s. <; ami f>. 



Cotlunorchis octnetlrus, HAFCKK.L, 1879, Syst. Jrr MrtliiM-n. p. 51. 



Sloniolocn austrtilis, MAYKR, 1900, Bull. Mus. (.'nrn|'. /.mil. .it Harvard College, vol. 37, p. 32, plate I, lii;. i; lintl., 1904, 

 Mrin. Nat. Sci. Brooklvn Inst. Museum, vol. i, p. 9, platr i, fig. 9. 



The following description is derived from studies of specimens found in the Baham.is. 

 and at Tortugas, Florida. 



Immature nirJ/isn (plate 11, fig. 6). Bell about 2.5 mm. high and with well-developed, 

 sharp-pointed, apical projection upon aboral side. Bell-walls thin.' There are 2 radially 

 situated, diametrically opposed tentacles, each about as long as the bell-height and with 

 long hollow, tapering basal bulbs. There is a single, ectodermal, orange-colored ocellus upon 

 the outer side of each tentacle-bulb near its point of origin from the umbrella. In addition to 

 the 2 long tentacles there are 2 short, rudimentary tentacle-bulbs go from the long tentacles. 

 Each of these rudimentary tentacle-bulbs has an ectodermal, orange-colored ocellus upon its 

 outer side, and there are 4 other ocelli upon the bell-margin in interradial positions. There 

 are thus 8 ocelli in all, 4 on the tentacle-bulbs and 4 interradial ones on the bell-margin. 'I he 



