MEDUS.E. I. 



59 



Table VI. Synopsis of the Genera of Mitrocoiin'da Torrev. 



Genera 



Cosmetirella Browne 



Cosmetjra (Forbes Hartlaub , 



Tiaropsis Romanes 



Mitrocoma Haeckel 



Halistaura Bigelow , 



Halopsis Agassiz 



-{- = present ; ~ ^^ absent. 



Number of 

 radial canals 



4 

 4 

 4 

 4 

 4 

 [2 — 16 or more 



Cirri 



+ 



Strictly spoken, the "cirri" of Cosinetira should not be called with tliat name, as they are 

 comparatively short and rigid and may not be coiled up spirally; they ouj^ht, as stated by Hartlaub 

 (1905), be designated as dwarf-tentacles. 



Genus Mitrocoma Haeckel. 



Mitrocoma polydiademata (Romanes). 



Tiaropsis polydiadeiiinfa Romanes 1876 a, Prelim. Observations on the Locomotor System of Mcdusre. 



— Philos. Trans. Roy. Soc. London. Vol. 166. — p. 274. 

 Tiarops — Romanes 1876 b, Some New Species, Varieties and Monstrous Forms of Me- 



dusae. — Jonrn. Linn. Soc. London. Vol. XII. — p. 525. 

 Tiaropsis — Romanes 1877, do. (plates). — ibid. Vol. XIII. — p. 194; PL X\', fig. 3. 



Mitroconiella polydiadcina Haeckel 1879, System der Medusen. — p. 185. 



— — Browne 1895, Medusae, L. M. B. C. District. — Proc. Tran.s. Liverpool Biol. 



Soc. Vol. IX. — p. 279. 



— fiiha Browne 1903, Medusae from Norway and vSpitzbergen. — Bergens Museums Aarbog 



1903- - P- 17- PI- \ fig. 3; PI. HI, figs. I, 3. 



— poLydiadeiiiafa Browne 1905 a, Medusje, Firth of Clyde. — Proc. R. Soc. Pxlinb. — p. 767. 



— polydiadema Browne 1910, National Antarctic H.xped., Nat. Hist. \'ol. V. — p. 33. 

 Mitrocoma polydiademata Mayer 1910, Medusae of the World. — p. 290. 



Mitrocomella — Bedot 191 2, Histoire des Hydroides, 4"'" periode. — p. 414. 



Umbrella nearly hemispherical, 12 — 22 mm wide. Stomach small with a cross-shaped base and 

 4 short, folded lips. Gonads linear or somewhat sinuous, extending along the outer three-fourth of the 

 4 radial canals. About 48 long tentacles with conical basal bulbs; numerous long marginal cirri; 16 

 open marginal vesicles; no ocelli. Manubrium, gonads, and tentacular bulbs red or yellowish-brown. — 

 Hydroid unknown. 



Haeckel introduced the s,^&\X\\\<g polydiadema, but Romanes called \\. polydiademata in all 

 of the four papers in which he mentioned the species. 



Romanes mentions this species for the first time in his preparatory work on the locomotor 

 system of the medusa; (1876 a) and describes it in the other paper of the same year (1876 b). Romanes 



