EEPORT THE TETSTICATA. 
247 
about 4 mm. in length and scarcely 1 mm. in greatest breadth. The post-abdomen is 
much narrower than the anterior portion of the body, but the thorax and abdomen are 
not distinctly separated. 
The Test is moderately firm and tough. There is a certain amount of incrusting and 
imbedded sand, but not sufficient to render the mass stilf or brittle. In the interior of 
the colony the test is of a fight grey colour and semi-transparent. The matrix is clear 
and structureless. The test cells are not very abundant, and are mostly small but 
irregrdar and much branched forms. No bladder cells are present. 
The Mantle is strong and the musculature is well developed. Over the anterior part 
of the body both longitudinal and transverse muscle bands are present, while in the post- 
abdomen they are aU longitudinal and are rather closely placed. 
The Branchial Sac is large and well developed. The transverse vessels are 
moderately wide and are provided with muscle fibres. The stigmata are fairly loug and 
are placed with regularity. 
The Tentacles are long and thin. They are of two sizes. 
The Alimentary Canal is relatively of very small size, and forms a short loop. 
Tlte Post- Abdomen is long and narrow. 
Locality. — Torres Strait, north of Australia ; depth, 3 to 11 fathoms. 
Two colonies of this species were obtained in shallow water off Cape York at the 
northern extremity of Australia. They differ somewhat in shape, the one being ovate 
with the long axis vertical (PI. XXXI. fig. 13), and the other roughly hemispherical with 
the long axis horizontal. The dimensions given above are those of the former specimen, 
the latter measures 1’2 cm, in length, 2‘5 cm. in breadth, and 1'5 cm. in thickness. 
No common cloacal apertures are visible on either of the colonies. The Ascidiozooids 
are seen externally as small circular areas slightly elevated above the general surface 
(PI. XXXI. fig. 13), In some places the open branchial apertures are visible. The shape 
of the Ascidiozooid is remarkable. The thorax and abdomen form a single cylindrical 
mass, tapering posteriorly into the long narrow post-abdomen (PL XXXI. fig. 15, j^9.a6d). 
The amount of sand imbedded in the test is not nearly so great as in the case 
of some allied species {e.g., Psammaplidium spongiforme 2 CO(\ Psammaplidium suhviride). 
It is enough, however, to render the colony opaque and roughen its outer surface. Some 
of the test cells are very coarsely granular, and a few are slightly pigmented. The trans- 
verse muscle bands in the mantle are very well marked (PI. XXXI. fig. 15, m.). The 
lobes around the branchial aperture are distinct, and the sphincter is well developed 
(PI. XXXI. fig. 15). 
The endostyle is narrow, but has a very undulating course. In the young 
Ascidiozooid, however, where there are only three rows of stigmata in the branchial 
sac, the endostyle is quite straight (PI. XXXI. fig. 16, en.). The interstigmatic vessels 
