EEPOKT ON THE TUNICATA. 
285 
The Ascidiozooids are fairly large and numerous. They are very conspicuous exter- 
nally, but are not arranged in definite systems. No common cloaca! apertures are present. 
The bodies of the Ascidiozooids are short, and are di^nded into thorax and abdomen. 
The Test is rather soft, and tears easily. It is of a greyish-white colour, and is nearly 
opaque. The matrix contains small test cells and numerous calcareous spicules. There 
are no bladder cells. The spicules vary somewhat in size. They are of rather regular 
stellate forms. 
The Mantle is fairly muscular. The branchial sphincter is well developed. 
The Branchial Sac is small. It has three rows of small but regularly arranged 
stigmata. 
The Alimentary Canal is rather large. The stomach is globular and smooth-walled. 
Locality. — Station 311, January 11, 1876 ; lat. 52° 45' 30" S., long. 73° 46' 0" W.; 
depth, 245 fathoms ; bottom, blue mud ; bottom temperature, 46° F. 
Several small colonies of this species are attached to a worn fragment of Coral trawled 
at Station 311, at the western end of the Strait of jMagellan, from a dej)th of 245 
fathoms. The dimensions given above are those of the largest colony, the others are 
considerably smaller. They are all incrusting forms (PI. XXXIX. fig. 16), and resemble 
the specimens of Leptoclinum teniie closely in their external characters. The colour, 
however, is distinctly greyer, and the Ascidiozooids are rather larger, and are placed 
further apart in the present species. The arrangement of the spicules in the surface layer 
of test is quite different in the two cases (compare figs. 10 and 17 in Plate XXXIX.). 
In the present species they are uniformly distributed, except immediately around the 
branchial apertures, where they are more numerous. The edges of the six lobes are 
especially strengthened by closely placed spicules. The branchial apertures are regularly 
six-rayed (PI. XXXIX. fig. 17, hr.). 
The spicules are mostly stellate, with many narrow pointed rays (PI. XXX IX. fig. 20). 
Some, however, have the rays shorter and broader so as to produce a more nearly 
spherical form of spicule. The test cells are very inconspicuous. Most of them are small 
and rounded, but a few elongated and some larger branched forms occur. 
The thorax and abdomen in the body of the Ascidiozooids are distinctly separated 
(PI. XXXIX. fig. 18), and are of about the same size. There are two strong retractor 
muscles, one running backwards on each side from the branchial sphincter, along the 
dorsal edge of the thorax. 
The transverse vessels of the branchial sac are narrow (PI. XXXIX. fig. 19, tr.) ; they 
are usually of the same size as the fine longitudinal vessels. The ciliated cells bounding 
the stigmata are distinct (PI. XXXIX. fig. 19, sg.c.). The endostyle is very large and 
conspicuous (PI. XXXIX. fig. 1 8) ; its course is straight. 
The alimentary canal forms a wide loop. The oesophagus leaves the dorsal edge of 
the posterior end of the branchial sac, and runs directly backwards to the large smooth- 
