TRACHYMEDUSAE — M.EOTIAS. 369 



GENERIC CHARACTERS. 



Petasidae with 4 radial-canals and with blindly ending centripetal canals which arise 

 from the ring-canal. Numerous tentacles which arise at equal intervals from the bell-margin. 

 4 lips, 4 radial-canals, 4 gonads. Development unknown. 



Ostrooumoff states that this genus resembles Olindias, but that the tentacles are all of one 

 sort, the stiff, laterally projecting tentacles being absent. His description and figure fail to 

 demonstrate the presence of adhesive disks on the tentacles, and I am inclined, with Browne, 

 to consider this genus to be more nearly allied to Agltiuropsis than to Olindias. 



Maeotias inexspectata Ostrooumoff. 



Manillas inexspectata, Ostrooumoff, 1896, Zool. Anzeiger, Bd. 19, p. 30; 1896, Bull. Acad. Imp. Sci. St. Petersbourg, ser. 5, 



tome 4, p. 402, plate 1, figs. 1, 3. 

 M.rolias inexpeclata, Browne, 1904, Fauna and Geog. Maldive and Laccadivc Archipelagoes, vol. 2, p. 736. 



Bell half-egg-shaped, 28 mm. wide, 21 mm. high. Very numerous (300) tentacles thickly 

 set around the margin; with well-developed basal bulbs and slender, filiform shafts; more 

 than 3 times as long as the bell-height. About 100 marginal clubs and 200 lithocysts. Velum 

 very wide. 4 straight, narrow radial-canals and 13 to 15 blindly ending centripetal vessels in 

 each quadrant. Of these, 3 are three-fourths as long as the radial-canals, 4 are about half, 

 and 8 about one-third as long as the radial-canals. All are straight and slender. Stomach 

 without a peduncle and with 4 long, folded, lanceolate lips, which reach level of velar opening. 

 The 4 ribbon-like, sinusoidally folded gonads are developed upon the entire lengths of the 4 

 radial-canals. Marginal clubs dark-red. Found in the estuaries of the Don and Kuban Rivers, 

 Sea of Azov, Russia. 



If there be suctorial disks upon the filiform tentacles, this medusa belongs among the 

 Olindiadse and is closely related to Olindias. Ostrooumoff, however, does not mention suc- 

 torial disks and his figures do not show them. 



Family LIMNOCNIDID^. 



The only species of this family is the remarkable fresh-water medusa, Limnocnida tan- 

 ganjicte Gunther, of Lake Tanganyika, Victoria Nyanza and the Niger, Central Africa. 



FAMILY CHARACTERS. 



Trachymedusae with 4 to 6 simple radial-canals. Numerous simple, hollow tentacles, 

 which project from the sides of the exumbrella above the bell-margin. Numerous inclosed 

 lithocysts on the exumbrella side of the velum. Gonads diffusely developed in the ectoderm of 

 the stomach-wall. Mouth a simple, round opening. 



Gunther states that the concretions are of entodermal origin, but Goto, 1903 (Mark Anni- 

 versary Volume), states that Gunther' s earliest stage in the development of the lithocysts is too 

 far advanced to be of value in determining this point, and he reasons by analogy with Ohndi- 

 oides that the concretions may be of ectodermal origin, and the medusa would then be one of 

 the Eucopidas, whereas Gunther places it among the Trachymedusae. In 1907, however, 

 Gunther repeated his observations and decides that the axial cells of the sense-organs, and 

 hence the concretions, are entodermal. 



This medusa has no place in Haeckel's system. It has the diffusely developed gonads upon 

 the stomach-wall and the round mouth-opening commonly seen in Narcomedusae, but its 

 hollow tentacles and inclosed lithocysts throw it out of this order. Its hollow tentacles and the 

 gonad encircling the stomach-wall are characters of the Anthomedusae, but the lithocysts pre- 

 vent its being placed among these medusae. It can not be placed among the Leptomedusae, 

 for its gonads are not developed upon the radial-canals, and indeed its entodermal concretions 

 and general appearance oblige us to classify it among the Trachymedusae in close proximity to 

 the Olindiadae. 



It appears to be a highly specialized form which has departed so widely from the type of 

 its salt-water ancestors as to baffle one in any attempt to determine with certainty its closest 

 living relatives. Unfortunately for such purposes, the sexual development remains unknown. 

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