198 
THE VOYAGE OF H.M.S. OHALLENGEE. 
The Test is very solid, and is nearly quite opaque. The matrix is crowded with test- 
cells. 
The Mantle is thin but fairly muscular. The muscle bands are very delicate, and run 
mainly in a longitudinal direction. The branchial sphincter is fairly strong. 
The Branchial Sac is of moderate size. The transverse vessels are all equally wide. 
The stigmata are large and well developed. They are wider than the fine longitudinal 
vessels. 
The Dorsal Lamina is represented by languets. 
The Alimentary Canal is large. The stomach is very long, and is smooth walled. 
Locality. — Eoyal Sound, Kerguelen Island ; depth, 20 to 60 fathoms. 
The small colony placed in this species resembles Amaroucium IcBvigatum in its 
general appearance and in the solidity of the test, but differs from it in several points 
in the structure of the Ascidiozooids. It is a small nearly globular colony (PI, XXV, 
fig, 10), which was obtained at Eoyal Sound, Kerguelen Island. It is of rather a dark 
colour, having a distinctly brown tinge, and is nearly opaque, the Ascidiozooids only 
showing through faintly even where they are close to the surface (PI, XXV. fig. 10). 
A good deal of the irregularity of the specimen is due, I believe, to contraction on being 
put into alcohol ; the shape was probably more nearly spherical when living. The 
Ascidiozooids are placed at various angles to the surface, and their bodies are found 
traversing the centre of the colony in all directions. The thorax of this species bears 
considerable resemblance to that of Distaplia rosea amongst the Distomidse. 
The test is very stiff and tough, not only on the external surface, but all through. 
It is very densely crowded with test cells, and these are rather larger than usual, and 
very granular. This causes the great opacity of the test. There are no bladder-cells and 
no vessels- 
The mantle has a very delicate but fairly abundant musculature. On the post- 
abdomen the bundles are closely placed. The branchial aperture has six triangular 
lobes ; the atrial aperture is prominent, and has a large rounded atrial languet (this was. 
not visible in the Ascidiozooid figured, PL XXV. fig. 11). 
The branchial sac is well developed. There are usually seven or eight rows of 
stigmata. The ciliated cells on the edges of the wide stigmata are large and conspicuous. 
The transverse vessels are wide and have horizontal membranes (PL XXV. fig. 12, tr. 
and h.m.). The tentacles are not numerous. The endostyle is conspicuous (PL XXV. 
fig. ll,ew.). 
The alimentary canal forms a long narrow loop (PL XXV. fig. 11 , ah.). The 
oesophagus is a curved, funnel-shaped tube, which runs from the posterior end of the 
branchial sac to a point rather on the side of the stomach than at its anterior end. The 
stomach is very large, and is of an elongated, ovate form, the anterior end being wider 
