THE MEDUSA OF THE SCOTTISH NATIONAL ANTAKCT1C EXPEDITION. 183 



as long as broad, containing concretions. On the wall of this canal near the tentaculo- 

 cyst a small roundish swelling is present in the earlier stages, and a long ridge-like 

 swelling in the adult. It is probably a sensory pad. 



The medusa as it lies on its back in a basin, with the margin of the umbrella folded 

 inwards, shows very clearly the sixteen radial furrows on the periphery of the ex- 

 umbrella. These furrows are lines of weakness, for they reduce the thickness of the 

 marginal jelly. In two places the ocular lobe is completely isolated from the tentacular 

 lobe, the tearing asunder taking place along the furrow. The folding of the incurved 

 margin is similar to that described for specimen D. 



The tentacular lobes measure 55 mm. in breadth, and are about two and a half times 

 as broad as the ocular lobes. Their length is about 30 mm. In this specimen the 

 length of the tentacular and ocular lobes is about the same. In VANHOFFEN'S specimen 

 the ocular lobes are a little shorter than the tentacular. In most of the octants there 

 is no indentation between the tentacular and ocular lobes ; an even margin extends 

 from one ocular cleft to another. But in two places there are natural indentations 

 between the ocular and tentacular lobes, very much like the indentations drawn by 

 VANHOFFEN. Evidently there is a fair range of variation in the shape and size of the 

 marginal lobes, and taken by themselves they are not a specific character. The 

 marginal lobes and the surface of the ex-umbrella are quite smooth. Apparently the 

 warts conspicuous on the lobes in the early stages disappear before the medusa reaches 

 the adult state. 



The arrangement of the canals in the marginal lobes is similar to that in the earlier 

 stages, but there are more bifurcations. The canal system has been well illustrated 

 in VANHOFFEN'S figure. 



In Mr VALLENTIN'S manuscript notes I have found several references to Desmonema 

 in Stanley Harbour, from November 1898 to February 1899. During November large 

 and small specimens were very abundant, the largest being about 1 foot (300 mm.) 

 in diameter. At the end of December specimens up to 2 feet (600 mm.) in diameter 

 were abundant. Records show that large specimens were present in considerable 

 numbers during January and February. On 6th February thousands were stranded 

 on the shore after a strong wind. 



Family ULMARID^E. 



Pliacellophora ornata (Verrill, 1869). (Plate II. figs. 3-4). 



Callinema ornata, Verrill, 1869, p. 116. 

 Callinema ornata, Fewkes, 1888, p. 234, pi. vi. 

 Phacellophora omata, Haeokel. 1880, p. 643. 

 Phacellophora omata, Vanlioffen, 1906, p. 59, figs. 25-26. 



Station 98, lat. 34 2' S., long. 49 7' W. Surface. 28th December 1902. 

 A single specimen was taken at this station, which is about five degrees east of 

 Montevideo. It is unfortunately damaged, having completely lost the oral arms. 



(ROY. SOC. EDIN. TRANS., VOL. XLVI., 247.) 



