430 
CHARLES L. BOULENGER. 
The umbrella has a diameter of 6 mm. The manubrium, as 
in L. tanganicae, consists merely of a thin circular band 
measuring 2*75 mm. across its base, and the mouth is a wide 
circular aperture, the diameter of which is ouly slightly less 
than that of the whole manubrium. 
Four radial canals run from the base of this organ to the 
umbrella edge, the latter being provided with a broad, some- 
what muscular velum a little over 1 mm. in breadth. 
There are between eighty and ninety tentacles, which are 
arranged, according to size, in distinct series, the perradial, 
interradial and adradial ones being the largest. The umbrella 
edge of this specimen is much macerated, and it is impossible 
to make out the exact mode of origin of the tentacles or the 
arrangement of the marginal sense-organs. 
The second medusa, obtained in September of the same 
year, is of small size, measuring approximately 2*5 mm. in 
diameter; although badly broken it is in a much more satis- 
factory state of preservation and presents several features of 
great interest. 
The very different degree of contraction of both umbrella 
and manubrium renders the animal very unlike the individual 
just described. The umbrella margin is much contracted and 
this makes the medusa appear comparatively much higher, 
in fact almost hemispherical in shape. The manubrium also 
appears very different and has the shape of a truncated cone, 
the base of which measures about 1 mm. in diameter. 
The conical form of the manubrium is due to the contrac- 
tion of its oral extremity, and when this organ is viewed from 
below the mouth is seen to be almost completely closed, 
appearing as a small opening surrounded by the folded oral 
edge of the manubrium (PI. 42, fig. 1). 
In possessing an almost closed mouth this individual is of 
considerable interest, in all the described specimens of 
Lim nocnida tanganicae the mouth remained wide open, 
and previous writers have laid great stress on this character; 
thus Gunther refers to “the wonderfully large mouth which 
the short manubrium seems inadequate to close,” and 
