204 
THE VOYAGE OF H.M.S. CHALLENGER. 
and convex, the lower is smaller and slightly concave. The surface is even, but somewhat 
roughened all over. The colour is brown. 
The length is 1’6 cm., the breadth 2 ’2 cm., and the thickness 17 cm. 
The Ascidiozooids are fairly large and numerous. Two or three common cloacal 
apertures are visible on the upper surface of the colony, but the Ascidiozooids are 
scattered evenly all over the surface, and do not seem to be arranged in systems. The 
Ascidiozooids are about 9 mm. in length and 1'5 mm. in greatest breadth. The body 
is quite opaque, and is not distinctly divided into regions. A slight constriction separates 
the thorax from the abdomen. 
The Test is firm, and the outer layer is stiffened by imbedded sand-grains ; it is of a 
brown colour and nearly opaque. The inner part is of a light grey colour, and is more 
transparent. The test cells are numerous and generally much branched. No bladder 
cells are present. 
The Mantle is thick and very muscular. Both longitudinal and transverse muscle 
bands are present, and they are closely placed. 
The Branehial Sac is of moderate size. There are more than twelve rows of 
stigmata, and the transverse vessels are wide and all of the same size. The stigmata are 
long and narrow and are arranged with regularity. 
The Dorsal Lamina is represented by a series of languets. 
The TentOjcles are numerous and closely placed. They are of two sizes. 
The Abdomen is relatively of large size, and is very opaque. 
The Post- Abdomen is wide, but not very long. 
Loeality. — Royal Sound, Kerguelen Island, January 19, 1874 ; depth, 20 to 60 
fathoms. 
This species, of which a single colony was obtained in Royal Sound, Kerguelen 
Island, shows some resemblance to Morehellium giardi and Sidnyum pallidum, while 
it is very closely related to Aplidium leucophaum (pee p. 205). It seems, however, to 
be a distinct form. 
The colony is a rounded mass without a peduncle (PI. XXVIII. fig. 8), and the 
surface is slightly but evenly incrusted all over with fine black sand-grains, which make 
it rough. The colour is a rich brown upon which the anterior ends of the Ascidiozooids 
stand out as small round yellowish spots, tbe whole being slightly obscured and darkened 
by the adhering sand-grains (PI. XXVIII. fig. 8). 
The common cloacal apertures are circular and about 1*5 mm. in diameter. The 
anterior ends of the Ascidiozooids are remarkably evenly distributed over the convex 
upper surface of the colony, and no traces of any division into systems, or of regular 
grouping around the common cloacal apertures, are visible. 
The test is stiff" and opaque, and the outer layer is particularly hard. The test cells 
