MKDUS/E OF WOODS HOLE REGION. 5] 



Family JEQVOREIBJE. 



KEY I" THE i. i:\F.II \. 



A. Radial canals 8 or more, often lobed or forked near proximal ends Hofo 



B. Radial canals 12, manubrium very short ami flat, oral lobes long, simple or crinkled Stomdbrachium 



i ' Radial canals usually numerous, 16 to 32, sometimes 100 or more. 



1. Manubrium very short or even indistinguishable, with simply a crenulated era! margin Rliegmatodi s 



'J. Manubrium well developed, oral lobes plain Eguorra 



3. Manubrium large and with complexly plaited oral lobes Zygodactyly 



HALOPSIS A. Agassiz I L863). 

 Halopsis ocellata A. Agassiz. 



Halopsis ocellata A Agassiz, Pro dings Boston Society Natural History. Vol. IX, lsi',:;. p. 219: North American Acalepha , 



1865, p. 99. Haeekel, System dor Medusen" p. 217, 1879. 



Hell low ami evenly arched, 3 <>r 4 times as broad as high. Tentacles very numerous and capable 

 of great contraction and extension, with numerous alternating cirri. Radial canals 4 in young speci- 

 mens, increasing from 12 to 20 in adults. Otocysts large and numerous, composed of double rows of 

 i itoliths, and symmetrically disposed along the margin of the bell. Manubrium very short, with four- 

 lobed month. Gonads form elongate masses along almost the entire length of the canals. 



Agassiz has noted the occurrence of double manubria inspecimens of this form, particularly where 

 there is an extension of the gastric pouch in one plane of the medusa, attributes this appearance to 

 a tendency to or "beginning of transverse fission." This inference seems to me hardly warranted 

 without clearer evidence of such fission among medusas. I have occasionally found the same appear- 

 ance in smaller medusae, for example, Oa ania languida and Gonioni mus, in which so far as I am aware 

 there has never been noted any tendency to fission. G. T. Hargitt has found frequent examples of 

 such double manubria and months in individuals undergoing regeneration of excised parts. (Cf. 

 Biological Bulletin, Vol. IV, p. 6etseq.) 



Agassi/, has made observations upon the development of this species. (Cf. Proceedings Boston 

 Society Natural History, Vol. IX, p. 219.) 



Distribution. — Nahant, Mass., Bay (Agassiz). This medusa has not been taken at W Is Hole 



recently, nor elsewhere in the southern part of the region, so far as known to me. 



STOMOBRACHIUM Brandt (1838 

 Stomobracriium tentaculatum I.. Agassiz 



Stomobrachium tcntac datum 1,, Agassiz, Contributions to Natural History of United States, Vol. IV. 1862, p. 361. A, Agassiz, 



North American Acalepha-. 1866, p. 98. Haeekel. System dor Medusen, 1879, p. 224. 



Bell low, evenly arched; radial canals 12, gastric portion of manubrium very fiat, mouth with 4 

 rather triangular lobes which arc variously frilled or folded. Tentacles very numerous, but short and 

 devoid of any considerable contraction or extension. Gonads linear in form and disposed along the 

 several canals. Ontogeny unknown. 



Colors. — The medusa is almost wholly devoid of color. 



Distribution. — Massachusetts Bay i Agassiz). 1 have occasionally taken at W Is Hole what may 



have been fragments of the somewhat firm gelatinous portions of this medusa. 



RHEGMATODES A. Agassiz (1862). 



Rhegmatodes tenuis A. Agassiz. Text cut. 



Rhegmatodet A. Agassiz, in I.. Agassiz Contributions to Natural History oi United States, Vol IV, 1862, p. 361. 

 Rhegmatodes tenuis A. Ana-si/, North American Acalepha . 1865, p 95. Baeckel, System dor Medusen, p. 223, 1879. 



Bell ven* low and tlat with evenly rounded exumbrellar surface. Radial canals numerous, from 30 

 to 4(1 or more in mature specimens, mostly simple, but exhibiting numerous variations, as spurs, anasto- 

 mosing branches, etc. Marginal tentacles numerous and evenly disposed, rather filiform and capable of 



