10 PERCY SLADEN TRUST EXPEDITION 
of the canal and attaining a length nearly, if not quite, equal to that of the facial rays. 
The stronger development of these apical rays constitutes the only difference (and this 
is probably not constant) which I can detect between the Providence specimens of this 
species and those from Australia. As the spicules have not yet been properly figured 
I take the opportunity of doing so on this occasion. 
Previously known Distribution. Near Port Phillip Heads, Bass Straits; and 
Watson’s Bay, Port Jackson [Dendy 1892]; New Zealand [Kirk 1897]. 
Register Nos., Locality, dc. X1x. 4, xxm. 2, a number of specimens, all from 
Providence, 4.10.05, D. 4, 50—78 fathoms. 
Genus Leucetta Haeckel (emend.). 
Canal system leuconoid, with small, spherical or subspherical flagellated chambers 
irregularly scattered through the chamber layer. 
Section A. 
No oxea present. 
4. Leucetta chagosensis n. sp. 
(Plate 1, fig. 6; Plate 4, fig. 2.) 
There are five specimens of this sponge in the collection, but two of them (cx. 10) 
are perhaps parts of the same. 
The external form (Plate 1, fig. 6) is massive or encrusting, irregular, lobose, with 
rather large, scattered vents with slightly prominent margins. The thin dermal membrane 
covers over irregular, meandering subdermal cavities. 
All the specimens are of much the same size; CxIx. 11, which may be regarded 
as the type, measures about 27 mm. in length by 18 mm. in breadth and 12 mm. in 
greatest thickness. 
Texture fairly compact, firm and resilient, but friable. 
Colour in alcohol ranging from white to rather dark brown; in the latter case 
probably stained by other specimens. 
The canal system is typically leuconoid. The flagellated chambers are oval and 
measure about 0156 by 0°104 mm. in diameter. They are eurypylous and each one 
probably has several prosopyles. The thin, pore-bearmg dermal membrane overlies a 
system of subdermal cavities, which liein the rather thick gelatinous ectosome, but are not 
to be sharply distinguished from the rest of the inhalant canal system, consisting of wide, 
irregular canals or lacune. Similar wide exhalant canals or lacunz converge into the 
still wider oscular tubes, which are surrounded by a moderately thick layer of gelatinous 
mesoglcea resembling the ectosome. The oscula are variable in size, commonly from 1 to 
2 mm. in diameter. 
The main skeleton is confused, and consists of triradiate spicules densely and 
irregularly scattered throughout ectosome and choanosome alike. In the dermal 
