SPONGES FROM THE ABROLHOS ISLANDS. 511 
compact texture, and, above all, by the coring o£ the primary fibres by 
sand-grains, which indicates an approach to the Family Spongeliidse. 
Register JSos. and Localities. VI. 3, VI. ' 9, Sandy Isle ; IV. 4, Wooded 
Isle. 
45. SponCtBlia dakini n. sp. (PI. 25. fig. 11.) 
This most interesting specimen forms a very smooth encrustation (about 
0"65mm. thick), almost white in coloui-, over a considerable portion of the 
surface of a very fine specimen of Ancorina australiensis (PI. 25. fig. 11). 
There is a well-developed, minutely reticulate cortex, about 0'085 mm. 
thick, formed of sand and broken spicules, which gives the surface a very 
uniform appearance and presumably covers the vents, as these are not visible. 
The main skeleton consists of columns of broken foreign spicules of 
various kinds, but without visilile spongiu ; the columns ran vertically and 
sometimes appear to branch slightly as they approach the surface. 
The thin, transparent dermal membrane is pierced by numerous round 
inhalant pores, which measure up to 0'05 mm. in diameter ; usually there is 
only a single pore in each mesh of the cortex. Small subdermal cavities in 
the sand cortex lead into large subcortical crypts or inhalant canals in the 
clioanosome, the mesogloea of which is but feebly developed. The flagellate 
chambers are crowded together, sac-shaped, measuring about 0*06 mm. in 
diameter ; they are enrypylous and each has several prosopyles. Some of 
the larger canals appear to be surrounded by fibrous tissue ; these are 
probably exhalant. 
This species is at once distinguished by its thin, encrusting habit and its 
well-developed, reticulate sand cortex. 
Register No. and Locality. VI. 6 h, Sandy Isle. 
46. Psammopemma ceassum {Carter) var. 
Holopsamma erassa Carter [1885-6]. 
Psa?nmoj}emma crassum Leiidenfeld [1889]. 
The single specimen, which is 35 mm. in height, 20 mm. in width, and 
about 5 mm. in thickness, is erect, somewhat lamellar in shape, thickening 
considerably towards the base of attachment. The surface is uneven and 
sometimes rugose. Oscula are not visible. Colour in spirit light greyish 
brown ; texture hard, gritty, incompressible, but friable. 
There is a thin, pore-bearing dermal membrane, overlying large subdermal 
cavities in the ectosome, which is feebly developed, with collenchymatous 
mesogloea. The canal-system is lacunar ; the chambers, which have several 
prosopyles, are large, sac-shaped, measuring about O'l mm. in longer 
diameter, and eurypylous. The gelatinous mesogloea is fairly conspicuous ; it 
contains stellate cells and also bands of fibrous tissue. 
The skeleton consists of a dense mass of sand-grains and broken spicules 
with no recognisable spongin, interrupted by irregular patches of soft tissue 
more or less free from sand. 
