228 
THE VOYAGE OF H.M.S. CHALLENGER. 
about 2 mm. in length and considerably wider than either the abdomen or the post- 
abdomen. 
The Test is soft and gelatinous, especially on the upper wide part of the colony. It 
is of a hght grey colour and is transparent. The matrix is crowded with small test cells. 
No bladder cells are present. 
The Mantle is moderately strong. The muscle fibres are few in number but of large 
size. 
The Branchial Sac is large and well developed. There are a large number of trans- 
verse vessels. The stigmata are small but numerous. They are narrow with rounded ends. 
The Dorsal Lamina is represented by a series of tentacular languets. 
The Dorsal Tubercle has a small rounded aperture which leads into a fusiform cavity 
lying below the nerve ganglion. 
The Alimentary Canal is relatively of small size. 
The Post- Abdomen is narrow but of moderate length. It is very opaque except in 
the middle line where there is a clear undulating streak representing the lumen of the 
septum. 
Locality. — Station 311, January II, 1876; lat. 52° 45' 30" S., long. 73° 46' 0"W.; 
depth, 245 fathoms; bottom, blue mud; bottom temperature, 46° F. 
This species is formed for a single colony obtained at the western end of the Strait of 
Magellan from the considerable depth of 245 fathoms. It is allied to Amaroucium 
variabile and to some other species which were found at Kerguelen Island, but in much 
shallower water. 
The colony is somewhat club-shaped in form, but in place of standing erect and being 
attached by the base of the peduncle, it is recumbent, and is fixed to a broken shell by 
nearly the whole extent of one side (PI. XXIX. fig. 1 3). There is slight lateral compres- 
sion, the upper and lower sides, as the specimen lies, being flattened. 
The Ascidiozooids are very distinctly visible. In the upper part of the colony there 
are a few entire Ascidiozooids, while in the lower stalk-like part there are a large number 
of detached post-abdomens (PI. XXIX. fig. 13). These last are of an opaque dull 
yellowish-brown colour, and so give a darker tint to the lower part of the colony. 
The test is soft and transparent, and on the top of the colony has an irregular and some- 
what ragged appearance (PL XXIX. fig. 13). I think it is very probable that when the 
colony was collected, a number of the Ascidiozooids had recently died and been ejected 
from the test. Many of the small test cells are very much branched and prolonged into 
delicate tapering processes. 
The sphincter at the branchial siphon is feeble, and the branchial aperture is distinctly 
six-lo1jed. There is an atrial languet present (PL XXIX. fig. 15, at.l.). The stigmata 
in the branchial sac are very numerous (PL XXIX. figs. 14, 15) and of moderate length. 
