304 
THE VOYAGE OF H.M.S. CHALLEHGEK. 
surface, and are not arranged in definite systems. There are no common cloacal apertures 
visible. 
TJie Test is very hard and firm. It is of a dull whitish colour and is opaque through- 
out. The matrix contains numerous test cells and calcareous spicules. No bladder cells 
are present. The spicules are stellate and regular, but they vary a good deal in size. 
TlbS Mantle is rather thick, and the musculature is well developed. 
Tlie Branchial Sac is small, and the stigmata are inconspicuous. 
The Endostyle is very wide. Its course is somewhat undulating. 
Locality . — Port Jackson, Sydney, Australia; depth, 6 to 15 fathoms. 
One specimen of this species was dredged in Port Jackson, from shallow water. It 
is a small but massive colony, which has evidently been attached to some dome-shaped 
object, as there is a large hollow on the lower surface (PI. XXXVIII. fig. 19). The area 
of attachment is very smooth ; there are no projecting threads or tufts of test. The 
thickness given in the above description is measured across the base of the colony at right 
angles to the breadth. The distance from the point of attachment to the upper surface 
in the thickest place (the centre of the colony) is a little over 1 cm. The colour is a 
dirty cream tint ; it is a mixture of white, yellow, and grey, and is quite opaque. 
The Ascidiozooids are remarkably small, and are closely placed. They are not 
conspicuous, and show merely as minute depressions on the surface. In external 
appearance this species resembles Leptoclinum japonicum somewhat, but in that form the 
Ascidiozooids are much more distinct (see PL XXXIX. figs. 1, 2), 
The test is solid and is relatively of large amount (PL XXXVIII, fig. 20). It is 
densely crowded with test cells, which are of rather large size and of various shapes 
(PL XXXVIII. fig. 21, t.c.). The spicules are fairly abundant in the superficial layer of 
test, but are scarce in the deeper parts of the colony (see PL XXXVIII. fig. 20). They 
are not arranged so as to define the Ascidiozooid areas as in some other species, but are 
distributed quite irregularly. The spicules vary greatly in size (PL XXXVIII. fig. 21, sp.), 
but are always more or less stellate in shape. In some places the matrix is distinctly 
fibrillated, but as a general rule it shows no structure. Large ovate or rounded granular 
cells are also present (PL XXXVIII. fig. 2\,p.c.). These are pigment cells of a greyish- 
yellow colour, and they probably aid in rendering the test opaque. 
. The branchial siphon is small but well formed (PL XXXVIII. fig. 20, hr.). The 
aperture is circular, and the sphincter is well developed. The musculature in general 
is strong. Retractor muscles are present which run downwards into the test 
PL XXXVIII. fig. 21, v.ap.) 
The alimentary canal is small. It forms a narrow loop. 
A numljcr of large tailed larvae were found in the colony. They are imbedded in the 
lower part of the test below the bodies of the Ascidiozooids, These larvae have ellipsoidal 
