THAUMANTIAS QUADRATA., 43 
(24x 4+-4), extensile (but usually borne rather short), pale pinkish tentacula, with bulbous 
bases. The bulbs are ocellated, with dense crescentic masses of purple pigment-cells. 
When the margin is much magnified, it is seen to be bordered by a narrow band or thread of 
fibrous cells, from which the tentacles spring, and between each pair there are six or seven 
short, fine, secondary tentacles, without ocelli at their bases. The coloured bulbs of the 
larger tentacles are very conspicuous, and appear in the water as a circle of brilliant purple 
gems. The inner margin of the umbrella is bordered by a shelf-like veil. The sub-umbrella 
is depressed, and on its surface run the four radiating vessels with a long, linear, somewhat 
clavate ovary, of a bright pink colour, commencing very near the centre, and terminating close 
to the margin in the course of each. The stomach is very short, but wide, of a rose colour, 
and has four lanceolate, fimbriated lips, bordered by a compact edging of fibrous cells. 
This beautiful Medusa is very abundant in the bays and harbours of Zetland, especially 
in the Sound of Brassay, where it is the most common species of its genus. Mr. Alder met 
with it on the south coast of England, at Falmouth, in 1847. 
Plate VIII, fig. 1, a, represents its usual appearance, twice the natural size ; 1, b, as seen 
from above, of the size of nature; 1, e, an ovary; 1, d, a lip; 1, e, a pair of the larger ten- 
tacula with their ocelli, and the smaller tentacula between them. 
B. Marginal tentacles of one order. 
[THAUMANTIAS. | 
* Marginal tentacles, four. 
2. Thaumantias quadrata, Forbes. 
Plate IX, Fig. 2. 
Umbrella campanulate, rather elongated, becoming globose during contraction, smooth, 
pellucid, colourless ; margin with four equidistant tentacula springing opposite to the gastric 
vessels from large and conspicuous bulbs. The tentacula are rather stout, dusky purple, and 
conspicuously granulated on the surface. The bulbs are bright yellow, with ocelli composed 
of vermilion pigment-cells loosely grouped together. A similar ocellated bulb is in the centre 
of the marginal space between each pair of tentacles, but is not so large as those at their 
bases, and exhibits no rudiment of a tentacle springing from it. In the interspaces again, 
between each intermediate bulb and the tentacular one, is a very small yellowish tubercle, 
without an ocellus. I have no reason to think that tentacula are developed from any of the 
bulbs, except the four largest. The four ovaries are ovate, pale yellow, and placed in the 
course of the radiating vessels in the lower half of the sub-umbrella, towards the margin. The 
inner margin is surrounded by a veil. The proboscis is rather short, but slender and narrow, 
quadrangular, yellow, lineated with red. It terminates in four simple, triangular, acute lips. 
This little species was observed very abundantly in the harbour of Tarbet, Loch Fyne, 
in the autumn of 1845. The umbrella is scarcely more than two tenths-of an inch in length. 
Plate IX, f. 2, a, represents it of the natural size ; 2, b, magnified, and seen from the side ; 
2, ¢, as seen from above; 2, d, an ovary; 2, e, tentacle and its bulb, with the intermediate 
bulbs. 
