380 I-.!'!.!,;: TIN <>K THK TNITKI) STATUS nsii COMMIS:"*] 



Obelia commissuralis MrCr. Fig. n". 



tl'roo. ElliotI Soc.. vol. I. No. 1. p. l'J7.) 



Bell disk-shaped. Marginal tentacles l(i at time of liberation, long and slender. Ovaries not 

 developed at time of liberation. 



D:*trilnit:-i. . < o'.ouiea abundant in Wood.- Hole region, '.'rowing on piling of wharves and on 

 siibm'-r-rd timb.Ts gi aenilly. 



Obelia freniculata (I. inn.). Figs. ISdA, !!S. 



I S,':' ! '',''!f : " >, ::ii'u!<tti.l Linn.. Syst. Nitt.. p. HI'-'. I 



Bell disk-shaped, or shallow bowl-shaped. Marginal tenta- 

 cles LM at birth, each with an inward projei ting .--pur. Otoliths 8, 

 two bet we, 'ii each two radial canals, placed over the liases of the 

 tentacles and not between them. Proboscis short, with four 

 inconspicuous lobi'Jar lips. Radial canals 4. Ovaries oval, hang- 

 ing beneath the middle portion of the radial canals. No sense- 

 bulbs. Thi", like other species of Ohel'm, has the habit of swimming vvith the bell reversed, so that it 

 appears somewhat like an umbrella turned wrong side out. 



Co/or.--. ---The only color is in the light-yellowish ovaries ami proboscis. 



Jlixli'Hiiitinii. Abundant throughout Wood.- Hole region. 



Obelia loiigissima ( Pallas i. 



>, fnfnrin //^//s.W;//(i I 'a lla^. KlrMrlitis Zoopliytoruni, p. 1 1'.'. ) 



It isexceedinglv ditiicult, if not impossible, to differentiate the medusa' of the various species of 

 this genus. In sonr.' cases the only way to identify them is to see them given off from the hydroid 

 colonies. I know of no means of distinguishing this species from the preceding except that the ten- 

 tacles may be 20 instead of '24. 



IHsti'lbii'inii. The hvdroid colonies have been found at Woods Hole and off <iay Mead. 



Obelia flabellata (Winers) 1 Eueope polygenA A. Ag.?- 



Ann. anil MK. Nut. Hist.. :ld srrirs. vol. xvm. p. '7. -'North American Acalrplui. I 



lliffers from the preceding in no constant feature that I am aware of. 

 Dixlr'ilnitiuii. Woods Hole; off Thimble Island (Verrill). 



Obelia gelatinosa (Pallas) l = //i/(;ifin i/ii/miti'n A. Ag.'-' (Verrill). 

 (> frrtuldi-ia yrlittiiiHtn 1'illlns. Elunchii" Zoopliytorinn. p. llci. ^Xortli Anirric'all Aralrph;r. p. 94.) 



Bell disk-shaped. Tentacles 16 at time of liberation, each with an inward-projecting spur. 

 Otocysts 8, placed over bases of tentacles. Proboscis short, with mouth surrounded by four tabular 

 lips or mouth-arms. Radial canals 4. Ovaries round, hanging beneath middle part of radial canals. 



Otlor*. Ovaries and proboscis light-yellowish. 



Jtixtribiition. Colonies have been found growing at Xew Haven, Conn.; along the Rhode Island 

 coast, and in Vineyard Sound. 



Obelia dichotoma (Linn.). 



(Sniiilin-iu ilicliiilniiiii l.inn., Syst. Nut., p. 131'i> 



Bell very shallow, disk-shaped. Marginal tentacles 16 at time of 

 liberation. Not distinguishable from the preceding. 



Distribution. Colonies dredged off Gay Head, 1 fathom (Verrill). 



Oceania singularis Mayer. 



(Bull. Mus. Comp. Zool., vol. xxxvin, No. 1, p. 7. ) 

 99. Oceania singulars Mayer. 



Bell rather shallow, flaring decidedly at margin, and with a well 



marked dome-shaped apical projection. Marginal tentacles 16, each bearing a sense-bulb at ita base. 

 There are rudimentary tentacles between bases of larger ones. Proboscis not extending beyond 

 velum, and ending in four broad lobes or mouth-arms that are not fimbriated. Eadial canals 4, bear- 

 ing the ovaries on their upper portion. There is an otocyst between each pair of tentacles, including 

 the rudimentary ones. 



