REPORT ON THE MONAXONIDA. 75 



is tlie way in which two out of the three microsclera attach themselves to the skeleton 

 fibre. It is a rather remarkable fact that we can find no spicules which we can put 

 down as young forms of the large sigmata, except a very few, which somewhat resemble 

 them in shape and size but are much more slender, and appear as if they might form 

 links connecting the large with the ordinary, small sigmata. 



Locality. — Simon's Bay; depth, 10 to 20 fathoms. Three fragments. 



JEsperella hiserialis, Ridley and Dendy (PI. XIV. figs. 2, 3 ; PI. XV. figs. 8, 8a, 86). 



1886. EspereUa hiserialis, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. xviii. 



p. 340. 



Sponge (PI. XIV. figs. 2, 3) consisting of a long, slender axis, perfectly straight and 

 somewhat flattened in one plane, from which arise very short, slender, straight spicular 

 processes. These processes are arranged in two opposite series, at either end of the longer 

 transverse diameter of the sponge, forming on each side a single long row of closely placed, 

 hair-like projections. ■ The axis of the sponge is somewhat twisted, so that the two rows 

 are not quite straight. It is covered with a thin crust of brown, transparent tissue, 

 containing many spicules, and terminates abruptly at the lower end, having apparently 

 been broken oif short, while at the upper extremity it ends in a slightly rounded apex. 

 Length of sponge 92 mm. ; longer diameter 1 mm. Surface hispid. Dermal mem- 

 hrane fairly distinct. 



Skeleton. — ((() Dermal; from an imaginary line, drawn longitudinally down the 

 middle of each flattened side of the sponge, a large number of tylostylote spicules 

 diverge more or less at right angles towards either side. These spicules have their 

 bases placed along the middle line, while their apices are directed towards the bases 

 of the hair-like processes, which they are just about able to reach. This arrange- 

 ment is easily recognisable, though not very regular, for many of the spicules are placed 

 so as to project from the surface of the sponge, giving to it the hispid appearance 

 described. (6) Main; a central, dense spicular axis composed of very long styli firmly 

 united together, from two sides of which come ofl" short, hair-like fibres as already 

 described (the spicular processes). Outside the axis there are also longitudinal bands of 

 spiculo-fibre, apparently not arranged in any very definite manner. 



Spicules. — (a) Megasclera; of two kinds, (l) Very long, slender styli (PI. XV. 

 figs. 8a, 86), of extremely elegant shape, becoming gradually inflated in the centre, but 

 very thin at both ends. Apex not very sharply pointed ; no head. These spicules 

 may reach over 2 mm. in length, with a diameter in the middle of 0"038 mm.; they 

 occur only in the main axis. (2) Rather short tylostyli (PL XV. fig. 8), broadest near 

 the apex, each hastately pointed and with a distinct, elongated head narrowing towards 

 the top; size about 0'44 by O'Ol mm.; these occur in the dermal skeleton, in the 

 longitudinal fibres outside the axis, and in the hair-like projections. (6) Microsclera; 



