162 THE VOYAGE OF H.M.S. CHALLENGEE. 
3. Cladoxeas (PI. XYIIL figs. 4-9), of various forms. 
A. Of the body of the sponge. 
a. Orthotrisene, a conical, sharply pointed rhabdome, with conical, sharply pointed 
cladi, at first diverging outwards and forwards, but mostly outwards, and afterwards hori- 
zontally. Ehabdome 3'6 by 0‘05 mm., cladi 0'47 mm. long. 
Orthodisene (PI. XVIII. fig. 8), similar, but with one cladus aborted. 
y. Orthomonsene (PI. XVIII. fig. 9), similar, but with two cladi aborted. Rhabdome 
3'75 by 0'075 mm., cladus 0‘535 by 0'055 mm. This is by far the commonest form. 
B. Of the excurrent tube. 
а. Orthodisene, an orthotrisene with one cladus aborted, the remaining two some- 
times equal, oftener unequal in length ; when equal about I'O mm. in length, or longer 
or shorter according to the diameter of the tube which they support. 
;S. Orthomon^ne (PI. XVIII. fig. 4), similar, but with a second cladus aborted, or 
reduced to a tubercle, and the third much developed, attaining a length of IT 43 mm. 
y. Diehomonsene (PL XVIII. fig. 6), similar to yS, but with the remaining cladus 
bifurcated, one of the deuterocladi being large and the other scarcely more than a 
tubercle. Rhabdome 5 ’5 33 by 0 '05 mm. ; relative lengths of protocladi and deuterocladi 
very variable; the protocladus frequently I'O mm., the large deuterocladus 0'7 mm., the 
reduced deuterocladus 0'07 mm. long. 
The measurements of these spicules are taken from examples obtained from an 
excurrent tube about 5 mm. in diameter, belonging to a sponge about. 20 mm. in 
diameter. In a tube of about twice the diameter of the preceding, the cladi of the 
spicules are frequently much longer, e.g., 2T42 mm., with about the same thickness. 
II. Microscleres. 4. Oxy aster (PI. XVIII. fig. 12), minute, with a comparatively 
large centrum, and numerous slender, sharply pointed actines; 0‘008 to 0'0118 mm. in 
diameter. 
5. Sanidaster (PL XVIII. fig. 11), similar in form to that of Tribrachium schmidtii, 
but larger; O’Ol 185 to 0 '01 58 mm. long. 
б. Orthodragma (PL XVIII. fig. 13), chiefly confined to the oscular tube; of the 
usual characters; 0‘0237 to 0‘0276 mm. by 0'0118 mm. 
Colour. — Translucent greyish-white, choanosome opaque yeUowish-white. 
Habitat. — Torres Strait, August 1874 ; depth, 3 to 11 fathoms. 
Station 188, Arafura Sea, south of Papua, September 10, 1874; lat. 9° 59' S., long. 
139° 42' E. ; depth, 28 fathoms; bottom, green mud. 
Also (Ridley) Port Darwin, 7 to 12 fathoms; bottom, sand and mud; and Torres 
Strait,. 10 fathoms ; bottom, sand. 
Remarks.-^As one of the most remarkable sponges, if not the most remarkable, 
of the Tetractinellid collection, this species merits a detailed description. The first 
