24 DISCOVERY REPORTS 



families. It differs, however, from the Calycopsidae in the possession of a gelatinous apical projection, 

 a well-developed gastric peduncle, four finger-shaped oral tentacles, a pair of small marginal tentacles 

 adjacent to each of the large tentacles, and the presence of an ocellus on each of these latter. Unfor- 

 tunately the distal parts of the tentacles are missing in all the specimens, so that we do not know 

 whether they have a terminal knob of nematocysts as in the Calycopsidae. In spite of the presence 

 of oral tentacles above the mouth and the grouping of the marginal tentacles, Riissellia is widely 

 separated from the Bougainvilliidae, in which the corresponding organs have an entirely different 

 structure, and these same features separate it also from any other family of Anthomedusae. 



I have great pleasure in naming this genus in honour of the author of many papers on medusae, 

 my friend F. S. Russell. 



Russellia mirabilis gen.n., sp.n. 

 (Plate IV, figs. 1-6, text-fig. 4) 



Occurrence: WS 300. 5. x. 28. 55' 07' 30" S, 31^ 56' 55" W. Between South Georgia and South Sandwich 



Islands. Net: N 100 B loo-o m. i specimen. 

 St. 584. 13. i. 31. 67° 26' 45" S, 69° 35' 15" W. West of Graham Land. Net: N 100 B 165-0 m. i specimen. 

 St. 587. 13. i. 31. 66° 28' 30" S, 71° 16' 15" W. West of Graham Land. Net: N 100 B 400-120 m. i specimen. 

 St. 1871. 12. xi. 36. 64° 04' 24" S, 52° 57' 30" W. East of South Shetland Islands. Net: TYFB 1450-1000 m. 



I specimen. 



The specimen from St. 587 is chosen as the holotype. 



The umbrella (PI. IV, fig. i) is 9 mm. in diameter and about 15 mm. in height, of which the broad, 

 dome-shaped apical projection occupies about one-third. Lateral walls moderately thick, the lower 

 margin hanging in lobes somewhat below the level of the ring-canal. The stomach is mounted on a 

 broad, conical peduncle, about 2 mm. in length, which extends partly into the cavity of the stomach. 

 The base of the stomach is cross-shaped; the stomach itself is deeply folded inward in the interradii, 

 and in one of the specimens also in the perradii. In the preserved condition the stomach is slightly 

 wider than long, its length somewhat less than half the height of the bell cavity. The interior surface 

 of the stomach is densely wrinkled transversally, and along each interradius is a narrow, prominent 

 ridge thrown into regular transverse folds (PI. IV, fig. 2), indicating that in living specimens the 

 stomach may be extended to a greater length. The gonads are adradial, separated in the perradii 

 and interradii by narrow lines. They occupy the entire length of the stomach, and their surface is 

 smooth, without transverse folds. 



The mouth tube is very short, the mouth quadrangular with very short and simple perradial lips. 

 The mouth rim is smooth and entire, slightly thickened (PI. IV, fig. 3) ; there are no nematocysts in the 

 rim itself, but some few are scattered in the wall above it. At a short distance above the perradial corners 

 of the mouth are four oral tentacles (PI. IV, fig. 3), finger-shaped, tapering towards their distal end; 

 they have no terminal cluster of nematocysts, but numerous nematocysts are evenly scattered 

 throughout the entire length of the tentacle, no more densely towards the tip than in the basal part. 



There are four radial canals. Their ascending part, on the peduncle, is fairly wide, in transverse 

 section like an equilateral triangle; the descending portion on the subumbrella is narrow and flat, 

 with smooth edges. Ring-canal narrow. Velum narrow. 



There are eight large tentacles, four perradial and four interradial, of equal size (PI. IV, figs. 4-6). 

 The basal part of each tentacle, the ' root ', is directed upward and outward and is deeply sunk into a 

 narrow fissure between two prominent lobes of the umbrella-margin. In the interradial tentacles the 

 ascending root is directly adnate to the gelatinous tissue of the exumbrella, in the perradial tentacles 

 the root is connected with the terminal part of the corresponding radial canal by a triangular split. 

 The free, filiform parts of the tentacles are only seen in one of the specimens (St. 584); they are very 



