132 
THE VOYAGE OF H.M.S. CHALLENGER. 
Ectosome. — The cortex, 0’48 to 0*63 mm. in thickness, much resembles that of Pilo- 
chrota Tiaeckeli ; the outer two-thirds, or 0*318 mm., is a collenchyma, containing long 
fusiform cells running in all directions, clusters of deeply stained granule-cells (PL 
XIV. fig. 37), and separately scattered cells, composed of faintly staining finely granular 
material lying in cavities of the collenchyma, and in some places so numerous as to 
constitute the greater part of the tissue. The chones, as usual in the genus, are irregular 
in form, traversing the cortex as canals of various diameter, and usually converted 
into a succession of vesicles by well-developed velar diaphragms. 
The flagellated chambers measure about 0*0276 by 0*02 mm. in breadth and length. 
Pilochrota anancora, Sollas (PI. XIV. figs. 16-22). 
Pilochrota anancora^ Sollas, Prelim. Account, Sci. Proc. Roy. DubL Soc., vol. v. p. 190, 1886. 
Sponge (PL XIV. fig. 16), small, spherical, depressed, free. A single oscule situated 
on one side of a membranous area or cloacal roof. Surface uneven ; pores large, in 
sieves ; situated in winding, channel-like depressions. 
Spicules. — I. Megascleres. 1. Oxea (PL XIV. fig. 17), varying from a somewhat 
stout, fusiform, usually curved, sharply pointed form, 1*68 by 0*023 mm., to a longer, 
slenderer, anisoactinate form, with its greatest diameter nearer the distal than the 
proximal end ; proximally attenuating, often to a filiform, excessively sharply pointed 
extremity ; distally variously pointed, excessively sharply or pencil-pointed, or rounded 
off close to the end ; 3*18 by 0*021 mm. 
2. Orthotrisene (PL XIV. fig. 18), a conical rhabdome, usually rapidly attenuating 
proximally to a filiform sharply pointed extremity ; cladi simple, straight, conical, sharply 
pointed. Ehabdome 1*63 by 0*0*276 mm., cladi 0*127 mm. long. 
II. Microsclere. 3. Chiaster (PL XIV. figs. 19, 20), a small centrum with numerous 
fine rod-like actines, terminally tylote; total diameter 0*0118 mm. 
Colour. — Cream-white. 
Habitat. — Bahia ; depth, 7 to 20 fathoms. 
Remarks. — The single specimen of this sponge measures 15 by 16 by 11 mm. ; the 
oscule is a little less than 1 mm., and the oscular membrane about 3 mm. in diameter. 
The latter is not fringed with oxeas as in Pilochrota purpurea. The ectosome (PL XIV. 
fig. 21) or cortex is about 0*72 mm. in thickness, the outer layer, for a distance inwards 
of 0*24 to 0*35 mm., excavated by wide somewhat irregularly shaped ectochones, the 
inner, 0*4 mm. in thickness, by the inferior cortical canal, into which the ectochones open,. 
The structure of the cortex resembles that of Pilochrota crassispicula, from which 
the present species is chiefly distinguished by the slenderness of the rhabdome of its 
orthotrisene ; it is possible that this character may not be of specific importance, 
