SPONGES FROM THE ABROLHOS ISLANDS. 493 
thickly scattered through the ectosome and choanosome, as well as forming 
a well-developed dermal layer. Large brown pigment grannies are 
scattered throughout all four specimens. 
The form and size of the spicules agree closely with Sollas's description 
of Carter's specimen. 
Previously known Distribution. Fremantle, West Australia (Carter). 
Register Nos. and Localities. VI. . 6 a, Sandy Isle ; I. 3, Turtle Bay ; 
II. 6, III. 6, Wooded Isle. 
17. Ancorina brevidens n. sp. (PI. 26. fig. 9.) 
The single specimen, which is about 60 mm. long, 40 mm. wide, and 
20 mm. thick, is massive and potato-shaped ; at one end is a group of 
about twenty small, close-set oscula, which average about 1 mm. in diameter. 
The surface is smooth, a large portion of it being covered with foreign matter 
of varying kind. Colour in spirit purplish grey; texture hard, compact, 
slightly compressible. 
The ectosome forms a cortex about 0'5 mm. thick, with numerous 
cortical crypts in its deeper portion ; the cortex appears to be only slightly 
fibrous, but contains numerous brown granular pigment cells, which occur also 
in the outer portion of the choanosome. 
The main skeleton consists of close-packed, radial bundles of oxea and 
trisenes ; the cladi of the trisenes occur at various levels in and just below 
the cortex, but chiefly just beneath the surface. The outer part of the cortex 
contains numerous comparatively small, slender, radially arranged oxea. 
There is a dense dermal layer of microrhabds, and both microrhabds and 
tylasters are abundantly scattered through ectosome and choanosome. 
Spicules : — (1) Orthotriaenes (PI. 26. fig. 9 a) ; shaft long, straight or 
slightly curved, tapering gradually to a fine point (sometimes blunted), 
measuring about 2-2 by 0"05 mm. ; cladi gradually but bluntly pointed, 
measuring about 0"16 by 0*04 mm. 
(2) Anatriasnes (PI. 26, fig. 9 b) ; shaft very long, slender, tapering verj' 
gradually to a finely pointed or blunted extremity, measuring about 3'0 by 
0'02 mm. ; cladi very much reduced in length, bluntly pointed, measuring 
about 0-026 by 0-017 mm. 
(3) Oxea of two sizes ; the larger (PI. 26. fig. 9 c) fusiform, curved, 
gradually and sharply pointed, measuring about 2'3 by 0'04 mm. ; the 
smaller (PI. 26. fig. 9 c') found only in the cortex, straight, sharp-pointed, 
measuring about 0'34 by 0"009 mm. 
(4) Microrhabds (PI. 26. fig. 9 d) ; roughened, slightly swollen in centre, 
measuring about 0"011 by O'OOS mm. 
(5) Tylasters (PI. 26. fig. 9 e) ; some have 6 to 8 slender rays with very 
small heads and no centrum ; others, which are slightly smaller, have more 
rays and a small centrum ; the average diameter of the entire spicule is 
0-013 mm. 
