THE CAMPANULAKID^ AND THE BONNEVIELLIDiE. 79 



OBELU CORONA Torrey. 



Plate 20, figs. 1-2. 



Ohelia corona Torrey, Hydroids of the San Diego Eegion, 1904, p. 14; 



Ohelia corona Mayer, Medusse of the World, vol. 2, The Hydromedusfe, 1910, p. 253. 



Obelia corona Fra.ser, "West Coast Hydroids, 1911, p. 38. 



TropTiosome} — Colony very small, about 4 mm. in lieight growing from a creeping rootstock 

 and symbiotic on a sponge. Stem short, monosiphonic, strongly flexuose or even geniculate, but 

 without the broad shoulder-like process upon which the pedicels are seated as in 0. geniculata. 

 There is a group of annulations just above eacli pedicel origin. Sometimes pedicels are borne 

 directly on the rootstock. . Pedicels alternate, usually sliort, consisting of 2 or 3 strong annu- 

 lations. The pedicels of terminal hydrothecas are long, sometimes twice as long as the liydro- 

 theca, with two or three annulations on the distal end and several on the proximal end, the 

 median part being smooth. Hydrothecse quite large, in proportion to size of tlie colony, deeply 

 campanulate, usually about twice as long as broad and with the margin ornamented by 10 or 

 12 well-marked bimucronate teeth which are well separated and clearly cut. The diaphragm 

 is well-marked and rather low. 



Gonosome. — The gonangia are borne both on the stem and creeping rootstock. They are 

 oblong-ovate in form, tlie distal end behig the broader and the proximal end narrowing to the 

 short annulated pedicel. There is a very short, inconspicuous collar and a very broad aperture. 

 The gonangia are about IJ times as long as the hydro thecse and contain typical medusfe. of the 

 genus Ohelia. 



Distribution. — The type-locality is the only one known, San Diego Bay, California, where 

 it is found on a sponge growiag on piles under wharves. 



Bathymetric distribution, 1 to 10 fathoms. 



I can not agree with Mayer when he says ^ referriug to this species "Probably a variety of 

 0. geniculata with toothed margins to the hydrothecse." On the contrary 0. corona bears but 

 little resemblance to the weU-known 0. geniculata when details are considered. It seems to 

 the present writer to be an unusually weU-defined species. 



OBELIA AUSTRO-GEORGIiS; Jaderhohn. 



Plate 20, figs. 3-4. 



Ohelia ausiro-georgix Jaderholm, Mitteilungen ueber einige von den Schwedischen Antarktischen Exped. 1901-03, 



eingesanunelte Hydroiden, 1904, p. vii. 

 Obelia austro-georgim Jaderholm, Hydroiden aus antarktischen und subantarktischen Meere, 1905, p. 17. 



Trophosome .^ — Colony (the basal part lacking) 8 mm. in height, stem simple, erect, and 

 curved with an abrupt bend opposite the origm of each branch or pedicel. Branchiag sparse 

 and irregular, the branches bearing the pedicels and curving abruptly above each pedicel base. 

 Both stems and branches bear well-marked groups of annulations above the branch and pedicel 

 origins, the number of annulations in a group being usually 5 or 6. The pedicels are quite 

 short and look hke the contuiuation of the branch from which they spring, this appearance 

 being due to the abrupt curve in the branches already referred to. The pedicels are usually 

 less than one-quarter the length of the hydrothecse and bear 3 to 6 strong annulations. The 

 hydrothecfE are rather large for this genus, rather slender, funnel-shaped; about twice as long 

 as wide at the margia. The margin is ornamented with about 14 sharply cut, turreted, or 

 rather, bimucronate teeth, between which sharply defined vertical liaes run down the hydro- 

 thecal wall sometimes for about one-quarter the length of the latter. These lines give a pleated 

 appearance to some of the hydrothecse. The diaphragm is somewhat obhque, in side view, and 



' Description of specimen kindly sent me by Doctor Torrey, the original describer of the species, from San Diego 

 Bay, the type-locality. 



^Medusas of the World, vol. 2, 1904, p. 242. 



■'' Description of a specimen (cotype) sent me by Dr. Elof Jaderholm and labeled "Obelia austro-georgise mihi, 

 Sudgeorgien, Cumberland Bay, 1902, Svenska antarkt, Exped." 



