HYDKOIDS OF THE WOODS HOLE REGION. 



351 



Obelia geniculata (Linn. ). = A'mv>yje diaphana L. Ag. (in part ).=.Eucope alternate A. Ag. Fig. 38. 



(Sertularia geniculata Linn., Syst. Nat., p. 1312.) 



'rm/ihoKimii', Colony usually consisting of a single geniculate stem bearing alternate pedicels on 

 broad shoulder-like processes. Pedicels short, usually with 4 to 6 annulations. Hydrothecte short, 

 campanulate or subtriangular. 



llonosoine. Gonangia long, tapering gradually to basal end and terminating in a collar which is 

 beveled and convex on its surface. Medusa; at liberation disk-shaped, with 24 marginal tentacles. 



Dixtriliiitifiii. Growing profusely on docks, floating seaweed, etc. One of the commonest species 

 in the Woods Hole region. 



Obelia gelatinosa (Pallas). = Lumnnlw g-igantea A. Ag. (ti'xte Verrill). Fig. 39. 

 (Sertutaria yelatiuosa Pallas, Elenchus Zoophytorum, p. 11C.) 



Troptiosome. Colony sometimes attaining a height of 15 to 20 inches, profusely branched in a 

 dendritic manner. Stem fascicled, with geniculate branches. Pedicels usually quite short, with 3 to 5. 

 annulations. Hydrotheae small, campanulate or sub- 

 triangular; margins armed with castellated or bimu- 

 cronate teeth. 



Gonoaome. Gonangia rather small, ovate, with 

 collared aperture. Medusas with 16 tentacles at time 

 of liberation (Hincks). 



Distribution. Shallow water, of ten bet weei 1 1 i d ( >w , 

 attached to timbers, etc. New Haven. Rhode Island 

 coast. Vineyard Sound. 



Obelia bicuspidata Clark. Fig. 40. 

 (Trans. Conn. Acad. of Sci., ill, p. 58. ) 



Trophosomr. Colony attaining a height of 

 about 33 inches. Stem fascicled, straight, irregu- 

 larly branched. Pedicels longer than in the next 

 species, and with 10 to 15 annulations. Hydrothecae 

 very deep, tubular, -their margins armed with bimu- 

 cronate teeth, between which lines originate which 

 pass down the surface of the hydrotheca:. 



Gonoxome. Unknown. 



Diitril>iiti<M.owd at a depth of 3 to 5 fathoms, from reefs near Thimble Island. Near Woods 

 Hole, 19 fathoms. 



Obelia longissima (Pallas).. Fig. 41. 

 (fSertularia hmgiiasiina Pallas, Elenchus Zoophytorum, p. 119.) 



Tmjilioxoiiie. Colony attaining a height of 12 to 14 inches. Main stem fascicled, flexuose, giving 

 off branches, which themselves branch in a palmate manner, the whole thus being subverticillate in 

 effect. Pedicels of varying length, usually extensively annulated. Hydrotherae rather deep, cam- 

 panulate, the margins appearing at first sight to be without teeth, but upon careful examination 

 proving to be armed with very shallow, regularly undulating teeth. 



Gonosfime. Gonangia ovate, with collared apertures. Medusa; at the time of liberation with 20 

 to 24 tentacles (Hincks). 



Distribution. Woods Hole. Off Gay Head. Dredged by the Fish Hawk at station 7051, about 40 

 miles southeast of No Mans Land ; depth, 3 fathoms. 



As described by Hincks, this species has not a fascicled stem. Authentic specimens from England, 

 however, have distinctly fascicled stems, and agree well with American specimens. 



Obelia bidentata Clark. 

 (Trans. Conn. Acad. of Sci., m. p. 58.) , 



Trophosome. Like that of (>. bizcuspidata, except that it attains a larger size, has shorter pedicels, 

 with 4 to .6 annulations, and proportionately wider hydrotheca?. 



40. Obelia bicuspidata 

 Clark. 



41. Obelia Ivngissimn Pallas. 

 A. Outline of ap orture of 

 hydrotheca. 



