30 SYDNEY J. HICKSON AND F. H. GEAVELY. 



The type of this species was found in South Georgia, in depths of 64-250 

 metres, and although the author gives no figures, we have no doubt of the identity 

 of our specimens with the type. 



FAMILY EUCOPIDAK 



GENUS OBELIA. 



Obelia geniculata. 



(Plate IV., fig. 30.) 



Sertularia genicitlala, Linnaeus, Syst. Nat. X. (1758), p. 812. 



Obelia r/enimlata, Hincks, Brit. Hyd. Zooph. (1868), p. 149, pi. xxv., fig. 1. 



Locality. Auckland Islands, off Port Ross, March 28th, 1904. 



This very widely distributed species was found in the material obtained from 

 the Auckland Islands. It has previously been described from numerous localities 

 north and south of, but not within, the tropics (10 : pp. 505-509 ; 3 : p. 23 ; 

 11 : p. 151). 



It is the only species of Hydrozoa in the collection that we have proved to 

 be phanerocodonic, and it is on that account noteworthy that, notwithstanding the 

 rich and varied hydroid fauna that was brought to light by the Expedition, not a 

 single specimen of this species was found under the ice in McMurdo Bay. 



A considerable number of luxuriant colonies were found growing on the frond 

 of a Laminaria. 



Dimensions. 



The height of the largest colony. . . 30 mm. 



Height of hydranths . . . . .0*4 mm. 



Length of pedicels of hydranths . . . ' 25 mm. 



Size of gonothecae . . . . 0'9 x 0'25 mm. 



Length of tentacles . . . . .0*4 mm. 



The specimens differ from the common British type of the species in having 

 two (instead of one) annular constrictions in the perisarc of the hydrocaulus above 

 each flexure. They also grow more luxuriantly and branch much more freely than 

 the British type. 



ffydrosome. Stem zigzag, sometimes pinnately branched, two deep constrictions 

 of the perisarc above each flexure. The perisarc below each flexure very thick, 

 forming a series of projections from which the short annulated pedicels arise. 

 Hydrothecae conical, somewhat longer than they are broad, margin entire, perisarc 

 thick. Tentacles of the hydranth about 30 in number. Gonothecse axillary, 

 urn-shaped, attached by a short annulated pedicel. 



Gonosome. Each blastostyle bears numerous young scattered medusae. 



