50 THE VOYAGE OF H.M.S. CHALLENGER. 



Tesserantha connectens, Hasckel (PI. XV.). 



Tesserantha connectens, Hreckel, 1879, System der Medusen, p. 375, No. 402. 



Umbrella helmet-shaped, one and a half times as high as broad, with conical apical 

 process and peduncle canal on the top. Exumbrella with eight longer and eight shorter 

 exumbral urticating ribs. Four double rows of gastral filaments along the four inter- 

 radial tseniola inside the central stomach. (Esophagus quadrangularly prismatic, half as 

 long as the height of the umbrella. Oral opening with four short, frilled, oral lobes. 

 Eight simple horse-shoe-shaped genitalia enclosing the small septal nodes in the con- 

 cavity of the arch. The eight principal tentacles (four perradial, four interradial) of ecpual 

 length, nearly as long as the height of the umbrella ; the eight secondary (adradial) 

 tentacles only half as long. Horizonal diameter of the umbrella, 6 mm. ; vertical 

 diameter, 9 mm. 



Habitat. — South-east part of the Pacific Ocean, not far from the island of Juan 

 Fernandez, lat. 33° 31' S., long. 74° 43' W.; Station 299. 14th December 1875. 

 Depth, 2160 fathoms. 



The umbrella (figs. 1-3) is highly vaulted, bell or helmet-shaped, rather constricted 

 beneath at the opening, just above the umbrella margin, and furnished above with 

 a pointed, conical, apical process which is nearly a third as long as the whole height of 

 the umbrella. It is about half as large again as the greatest horizontal diameter of 

 the umbrella above the umbrella margin. The exumbrella is distinguished by eight 

 projecting, strong, urticating ribs, four perradial and four interradial (figs. 1, er; 6, er). 

 These are sharp corners of the outer surface of the umbrella, almost triangular in 

 transverse section, which are armed with a broad streak of pigment cells and thread cells, 

 and stretch uninterruptedly from the point of the umbrella cone to the eight ocelli of the 

 umbrella margin, from which they pass on to the dorsal surface of the eight principal 

 tentacles. Eight secondary incomplete longitudinal ribs alternate with the eight prin- 

 cipal complete longitudinal ribs of the exumbrella ; these are much narrower and shorter 

 and only run from the bases of insertion of the eight adradial tentacles to half the height 

 of the umbrella (fig. 1 , er). 



The umbrella margin is somewhat contracted by a circular marginal stricture, and is 

 beset with sixteen tentacles, between which the gelatinous substance of the umbrella 

 projects a little in the form of short, roundish, solid, gelatinous lobes (figs. 1, 4, I). The 

 eight principal tentacles (four perradial and four interradial) are nearly as long as the 

 height of the umbrella, whilst the eight adradial or secondary tentacles alternating with 

 them, are only half as long. These also want the black roundish eye-spot (" ocellus," 

 fig. 1, oc) which is found at the base of the eight principal tentacles. These ocelli 

 consist of accumulations of black grains of pigment in the ectoderm of the tentacle 

 basis. All the sixteen tentacles are solid cylindrical filaments, gradually becoming 



