BROWNE— MEDUSA FROM THE INDIAN OCEAN 



173 



HYDROMEDUSJE. 



. . ANTHOMEDUSiE. 



Genus Euphysora, Maas, 1905. 



Hartlaub (1907) and Mayer (1910) agree in uniting the genera Euphysa and 

 Euphysora with Corymorpha. (Mayer uses the name Steenstrupia in the place of 

 Corymorpha ; the former is a medusoid generic name and the latter a hydroid generic 

 name.) I am in agreement with them so far as Euphysa is concerned, but am not, at 

 present, inclined to follow them in the case of Euphysora. 



Both Steenstrupia rubra and Euphysa aurata have one fully developed perradial 

 tentacle and three perradial marginal bulbs. The latter are called rudimentary tentacles 

 by the above authors, but it must be clearly understood that the tentacles have com- 

 pletely disappeared on the three bulbs. Far remote ancestors may possibly have had 

 four fully developed tentacles, but now only one tentacle remains, the others having their 

 former positions marked by the bulbs. 



It is known that Steenstrupia rubra is the medusa belonging to the hydroid 

 Corymorpha nutans. Hartlaub believes that Euphysa aurata is probably connected 

 with Corymorpha nana Alder, but at present there is no definite proof, though Mayer 

 records the connection as a definite fact. We have no clue to the hydroids connected 

 with Euphysora. 



The genus Euphysora was established by Maas for those Codonidse having four fully 

 developed tentacles, but one tentacle unlike the others being larger and different in 

 external appearance. 



There are three species belonging to this genus. The first was described by Bigelow 

 (1904, p. 251, pi. 1) from the Maldives under the name oi Euphysa tetrabrachia, and the 

 second by Maas from the Malay Archipelago under the name of Euphysora bigeloivi, and 

 this is the type species of the genus. Bigelow was doubtful about the generic position of 

 his new species, but Maas placed it in the new genus Euphysora and at the same time 

 pointed out the characters by which the two species could be recognised. 



Without going into every minute detail the two species can be easily distinguished 

 by the structure of their tentacles. Euphysora tetrabrachia has annular rings of nemato- 

 cysts on all the tentacles, but more on the longest tentacle. Euphysora bigeloivi has 

 large globular clusters of nematocysts on the longest tentacle only. Mayer is inclined to 

 regard the two species as being identical, for in his monograph (p. 37) he has written : 

 " Future studies will probably show that these distinctions are not of specific value, but 

 merely changes due to growth and variation, and that the two medusae are identical and 

 should be called Steenstrupia tetrabrachia." 



The third species, Euphysora valdivicB Vanhoffen (1911), has lateral branches on its 

 principal tentacle. This species I shall refer again to under Steenstrupia normani. 



