CORONATiE — ATOLLA. 



565 



This species is widely distributed over the North Atlantic. It has often been obtained 

 in open nets dragged at depths from 900 to 2,000 fathoms, but has also been taken occasionally 

 upon the surface, especially upon the Gulf Stream off the Carolina coast. It is a creature of 

 the deep ocean, not found in bays or estuaries, but is evidently a deep-sea medusa that may 

 only occasionally and under exceptional conditions come to the surface. 



When voung the 8 gonads are grouped in 4 interradial pairs, but in later life they swing 

 into adradial positions. The number of antimeres does not alter with age; but in some 

 specimens one finds some small tentacular pedalia inserted between larger rhopalar ones. 

 Vanhoffen records 11 specimens ranging from 5.5 to 114 mm. in diameter and with 18 to 24 

 tentacles. These were found by the f'aUivia in the Gulf of Guinea, west coast of Africa. 



Atolla bairdii forma valdivias Vanhoffen. 



Alalia valdjvia, Vanhoffen, 1902, Wissen. Ergeb. deutsch. Tiefsee Expedition, Dampfer Valdivia, Bd. 3, Lief, i, p. 15, taf. i, 

 fig. 5; taf. 5, fig. 21; taf. 6, fign. 41-46; taf. 7. — Maas, 1903, Scyphomedusen der Siboga Expedition, Monog. 11, p. 17, 

 taf. I, fign. 3, 4; taf. 3, fig. 23; taf. 12, fig. 108. 



Medusa 132 mm. in diameter. Central disk only half as wide as bell, smooth, without 

 radial furrows. 20 to 29 tentacles. The 4 interradial septal nodes of the subumbrella are 

 wider than in the typical J. hairdii. 9 specimens were found by the Valdivia in the Indian 

 Ocean. Maas records 9 specimens obtained by the Siboga m the Malay Archipelago. These 

 ranged from 12 to 82 mm. in diameter, the central disks ranging from 6 to 42 mm. in width; 

 and the antimeres range from 20 to 29 without reference to the size of the medusa. These 

 medusae were obtained from depths ranging from about 280 to 1,000 fathoms (see fig. 358). 



This form is very closely related to A. bairdn but the central disk is only half as wide 

 as the medusa, and the 4 septal nodes are wider than in A. hairdii. 



The Albatross obtained 3 specimens of this medusa in the Philippine Islands on April 10, 

 1908, at dredging station No. 5202. The characters and dimensions, in mm., of these specimens 

 are as follows: 



Specimen 



Specimen 



Specimen 



Exumbrella: 



Diameter of bell 



Diameter of central lens of exumbrella 



Width of annulus between coronal furrow and tentacular pedalia 



Width of tentacular pedalia 



Length of tentacular pedalia (in radial direction) 



Width of ocular pedalia 



Length of ocular pedalia (in radial direction) 



Subumbrella: 



Diameter to outer side of ring-muscle 



Width of ring-muscle 



Diameter to outer edge of gonads 



Diameter of manubrium 



Length (circumferential) of gonad 



Width (radially) of gonad 



General characters: 



Number of tentacles 



45-5 

 21.5 



'•5 



4 



3 



3-5 



7-5 



43 



Z.25 



3' 



■5 

 7 

 6 



H 



38 

 '9 

 1. 25 



35 



^•75 



3 



5 



35 



3' 



20. 



'3 



2. 



3' 



37 

 .8.5 



3-^5 



3 



2.5 



S-75 



34 



'4 

 3-5 

 3 



24 



Atolla gigantea Maas = A. bairdii (?) 



Atolla gigantea, Maas, 1897, Mem. Mus. Comp. Zool. at Harvard College, vol. 23, p. 80, taf. 12, fign. 2-4; taf. 13, fign. 7-9; 

 taf. 14, fig. 6. 



This form resembles A. valdiviiv, but the outer edge of the annular ridge in the ring-furrow 

 is notched, not simple and entire as in A. bairdii and A . valdivia-. Thus the central lens is half 

 as wide as the bell, as in A. valdiviir. Ring-furrow wide, and peripheral to it there is the 

 notched, annular ridge, and beyond this is the zone of pedalia and lappets. Tentacular pedalia 

 somewhat shorter and wider than the rhopalar pedalia. Medusa is 150 mm. wide. Num- 

 ber of tentacles ( ?) Gulf of Panama, Pacific coast of Central America (see fig. 359). 



Maas is uncertain as to whether or not the margin of the central lens is plain or notched. 

 Radial furrows of the ridge in the ring-furrow may be due to contraction in preservative fluids. 



