MEDUSAE. 149 



bulbs. Between two tentacles I counted the number of bulbs and sense-organs, and 

 found that there were 10 bulbs and 20 sense organs. The latter were arranged in 

 numbers thus: 1.1.2.3.1.1.1.2.2.2.2.2. From the examination of other groups of 

 sense-organs it may be said that there are either one or two, rarely three sense-organs 

 between every two bulbs. A sense-organ contains two otoliths. The figure (11) 

 shows the shape of the vesicle and the position of the otoliths, but the minute 

 details of structure are somewhat diagrammatic. 



It is impossible to estimate the number of tentacles, radial canals, &c, which the 

 specimen should have, as the fragments are only a portion of the whole medusa. 

 The tentacles are about 5 millims. to 8 millims. apart, and between them there are 

 about 8 to 12 marginal bulbs, and about 4 to 8 radial canals. 



Distribution : Indian Ocean. 



Order: TRACHOMEDUS^E. 



Family: OLINDIID^E, Haeckel, 1877; ex Browne, 1904. 



Gcmionemus, A. Agassiz, 1862. 



Gonionemus hornelli, n. sp. Plate I., fig. 6 ; Plate II., fig. 4. 



Description. Umbrella hemispherical, with moderately thick walls, about twice as 

 broad as high. Velum fairly broad. Stomach cross-shaped, having four perradial 

 lobes, situated upon a short, broad, cone-shaped peduncle. Mouth with four short 

 lips. Four broad radial canals, upon which are situated the gonads. Gonads small 

 in size, deeply folded and lobed, extending laterally from the canals and close to the 

 velum. Tentacles about 70, arranged in 16 groups, and all have an adhesive disc 

 about half-way down. Sixteen internal sense-organs, oval in shape, with a single 

 otolith. 



Size : Umbrella 6 millims. in width and 3 millims. in height. 



Locality : Pearl Banks, Gulf of Manaar. 



Notes. The single specimen is in an excellent state of preservation and in perfect 

 condition. The gonads are not papilliform, but are deeply folded and extend outwards 

 on both sides of the radial canals. They are about twice as broad as high, and contain 

 ova of a fan size. On one of the radial canals there is an additional gonad, smaller in 

 size, and not far from the stomach. It may be regarded as an abnormal growth, as 

 the other three canals show no signs of a gonad in that position. 



The tentacles are arranged in 16 groups, but the grouping is not so well marked as 

 in the genus Gossea. The tentacles forming a group are not of the same size, which 

 is due to development. The perradial and interradial groups each contain five 

 tentacles, the adradial four tentacles. The central tentacle in each group is the 

 largest, the tentacles on each side of the central one come next in size ; the two 

 outside tentacles vary very much in size, one is always very small. The attachment 



