MEDUSAE. I. 



77 



land it has also, however, been found on May 28th and June loth, and south-west of Ireland a spe- 

 cimen was taken on June i5th. Mature specimens have been found both at the end of May and in 

 the summer months. Quite young individuals have not been observed; from the present material we 

 can, therefore, state nothing more with regard to the breeding season, than that the spawning of the 

 eggs may take place during the summer. With regard to the further fate of the eggs and the hydroid 

 generation nothing can be stated. 



Genus Tiaropsis L. Agassiz. 



This genus was established by L,. Agassiz (1849, pp. 289 ff.) for the North American Tiaropsis 

 diademata L. Agassiz. Browne (1910, p. 33) characterises the genus in the following manner: 



"Mitrocomidcc with four radial canals; with eight sensory pits; with an ocellus adjacent to each sense 

 organ; without marginal cirri". - - The genus and its species have recently been dealt with by Browne 

 (1910, p. 33) and Bigelow (1913, p. 32). 



The genus comprises, probably, 6 species: multicirrata Sars in the eastern and western part of 

 the northern Atlantic and in the northern Pacific {diademata Agassiz and multicirrata Sars are identi- 

 cal, which shall be further demonstrated below); macleayi v. Lendenfeld (1884) from Australia; davisii 

 Browne (1902) from the Falkland Islands. Common for these three species is the possession of nume- 

 rous tentacles, all of the same size, whereas the three other species, all of which live in warmer seas, 

 have 48 well-developed tentacles and a number of rudimentary ones. The three species are the 

 following: Tiaropsis rosea Agassiz & Mayer (1899) from the Fiji Islands (Agassiz & Mayer 1899), 

 Malyan Archipelago (Maas 1905), and Tortugas, Florida (Tiaropsis diademata Fewkes 1882, Tiaropsis 

 punctata Mayer 1900); Tiaropsis mediterranea Metschnikoff (1886) from the Mediterranean; Tiaropsis 

 kelseyi Torrey (1909) from the San Diego region, Pacific coast of North America. 



The genus Tiaropsis has, thus, a very extensive geographical distribution. 



Tiaropsis multicirrata (M. Sars.) 



Plate IV, figs. 6, 7, 8, 9, 10; textfigs. II, 12, 13, 14. 

 Thaumantias multicirrata M. Sars 1835. Beskrivelser og lagttagelser ... p. 26. PI. 5, fig. 12 a c. 



melanops Forbes 1848. British Naked-eyed Medusae. -- p. 45. PI. X, fig. 3. 

 Tiaropsis diademata L. Agassiz 1849. Contrib. Nat. Hist, of the Acalephae of North America. -- p. 289. 



PI. 6, figs, i 18; PI. 8, fig. n. 

 Thaumantias eschscholtzii Haeckel 1879. System der Medusen. --p. 129. Taf. VIII, fig. 4. 



Bell flatter than a hemisphere, about 20 mm wide, gelatinous substance not very thick. Stomach 

 fairly small, provided with 4 folded lips; there is a broad, flat stomachal peduncle. 4 straight radial 

 canals, carrying the gonads, which extend from the base of the stomachal peduncle nearly to the cir- 

 cular vessel. About 300 short tentacles with well developed basal bulbs. 8 adradial, open marginal 

 vesicles, each containing about 12 concretions; at the base of each marginal vesicle there is a large, 

 black ocellus. Velum well developed. Stomach and gonads yellowish; the tentacular bulbs contain an 

 entodermal pigment mass and are also provided with fine ectodermal pigment granules. 



