MEDUSA. 47 



Distribution. Pacific Ocean : off the coast of Chile (Vanhoffen, 1892), off the 

 coast of Central America (Maas, 1897), off the Hawaiian Islands (Mayer, 1906), off 

 New Zealand (Haeckel, 1880). 



FAMILY ATOLLIM. 



Genus ATOLLA, Haeckel, 1880. 

 (sens. em. Vanhoffen, 1902, Maas, 1897-1904.) 



ATOLLA WYVILLII. 

 (Plate VII. , fig. 2.) 



Atolla Wyvillei, Haeckel, 1880, p. 488 ; id., 1882, p. 113, PL XXIX., figs. 1-9 ; Vanhoffen, 1902, p. 13, 

 Taf. V., fig. 22 ; Browne, 1908, p. 241 ; Bigelow, 1909, p. 39. 



There is one specimen of this Medusa in the ' Discovery ' collection. It was 

 taken in lat. 70 30' S., long. 169 E., off Admiralty Range (near Cape Adare), in a 

 trawl (bottom at 610 fms.), on 26th February, 1904, when the ship was among 

 pack ice. 



The aboral side of the umbrella is in good condition, but the oral side is damaged. 

 The stomach is torn, and only two of the gonads remain. The jelly is of a dark green 

 colour, which is clue to fixing with chromic acid, but the dark reddish "brown pigment, 

 which should coat the greater part of the umbrella, has been rubbed off, and only 

 traces of it now remain in grooves, depressions, and other more or less protected 

 places. 



This species has been very well described and figured by Prof. Haeckel. It is 

 distinguished from the other species of the genus by the presence of conspicuous 

 lobes, separated by broad furrows around the margin of the central disc of the 

 umbrella. The specimen shows this character very clearly. It has 21 lobes 

 separated from each other by a broad, deep U-shaped furrow. 



The width of the umbrella is about 77 mm. and the height about 20 mm. The 

 top of the central disc is probably not perfectly flat, but slightly convex ; its 

 diameter measured 46 mm. There are 22 tentacles and an equal number of sense 

 organs. The pedalia of the tentacles measured 6 mm. in length and 7 mm. in 

 width. The length of oesophagus is about 20 mm. The diameter of circular muscle 

 band is about 65 mm. 



Until Prof. Agassiz carried out in the 'Albatross' (1904-05) his explorations in 

 the Eastern Pacific, Atolla wyvillii was known from the Antarctic and sub- Antarctic 

 regions only. Mr. Bigelow (1909), in his report on the Medusae collected by 

 Agassiz's expedition, records specimens from the neighbourhood of the Galapagos 

 Islands, and from other stations. In the region explored Atolla occurs within 

 300 fms. of the surface. 



