AGASSIZ AND MAYER: ACALEPHS FROM THE FIJI ISLANDS. 175 
this individual the central mouth was still used for the capture of food. It 
seems probable that in those genera of Rhizostomæ that possess a single sub- 
genital space (the Monodenmia of Haeckel), the brachial disk has become 
separated from the floor of the sub-umbrella by the enlargement and final 
coalescence internally of the 4 sub-genital pits of the Semostome. 
Cassiopea ndrosia,! nov. sp. 
Plate 14, Figs. 45, 46. 
Generic Characters. Cassiopea, Péron and Lesueur, 1809. Discomedusæ 
without tentacles and without central mouth. There are 8 pinnately or tri- 
chotomously branching mouth arms, the lower or ventral surface of which is 
occupied by numerous suction mouths and vesicles. There are 4 sub-genital 
cavities, and 4 gonads. There are 12 or more marginal sense organs, and 
numerous anastomosing radial canals. 
Specific Characters. The bell is flat and disk-shaped, and 50 mm. in diameter. 
The number of marginal sense organs appears to be variable. In the specimen 
here figured there were 22, but in another individual there were only 18. 
Whatever their number may be, they are situated at equal distances one from 
another. There are 4 small sub-genital ostia. There are 8 pinnately branch- 
ing mouth arms, each arm being about 30 mm. in length. Their ventral sur- 
face is occupied by a great number of suction mouths surrounded by small 
tentacles, In addition to these there are also a large number of leaf-shaped 
vesicles scattered among the suction mouths. These vesicles are more numer- 
ous near the centre than they are at the free ends of the arms. The umbrella 
possesses two powerful sets of radial muscle bands. Twenty-two of these (in 
specimens with 22 marginal sense organs) are situated in the floor of the sub- 
umbrella, and radiate outwards toward the marginal sense organs.” An equal 
number are situated in the exumbrella, and alternate in position with the 
set in the sub-umbrella. The muscle bands of the floor of the sub-umbrella 
usually appear opaque and white in color, especially in states of contrac- 
tion. The muscles of the exumbrella, on the other hand, are deep blue- 
green. The general color of the umbrella is ashy brown. A large spearhead- 
shaped white spot is situated upon the radius of each sense organ at a little 
distange inward from the bell margin. Thus in a medusa with 22 marginal 
sense organs there are 22 of these large spots. The apex of each of these spots 
is directed outward toward the sense organ. Tn addition to these large spots 
there are usually 4 short white radial streaks between each pair of adjacent 
sense organs. There are numerous white spots upon the inner portions of the 
sub-umbrella, The upper fleshy portions of the 8 mouth arms are white or 
slightly grayish, The tentacles surrounding the suction mouths are deep brown 
in color, and the leaf-shaped vesicles are olive-green. 
1 Ndrosi is the native Fijian name for this species. 
