320 MARINE BIOLOGY OF THE SUDANESE RED SEA. 
Spicules. (Text-fig. 11.) 
The only spicules occurring in the sponge are oxea, 
and, though they vary very greatly both in length and 
diameter, there cannot be drawn any line of demarcation 
between the various forms. In this respect (though 
not in actual size) the spicules of HZ. bubastes are very 
like those of H. panicea, but the external surface of 
the two species is very different. As a general rule, the 
oxea are quite straight, but some of them are slightly 
curved, and when this is the case the curvature is always 
regular and extends throughout the length of the spicule. 
The spicules vary from 0:06 mm. to 0:13 mm. or even 
more, and in diameter from 0°001 mm. to 0°005 mm. 
The above species is a somewhat unsatisfactory one. 
The characters on which it is founded are, as in the case 
Fig. 11.— Halichon- of so many Halichondrias, of a very indefinite nature, and 
dria bubastes. no characteristic shape, or size, or skeleton can be assigned 
Spicules, x 500. to it. It does not seem to go into any of the previously 
named species very easily, however, and I have thought it 
better to add to the number of species in this already very confusing genus 
rather than assign it to any species not thoroughly agreeing with it. 
HALICHONDRIA sp. 
Three masses of calcareous worm-tubes were obtained, which are surrounded 
by an irregular sponge belonging to this genus. The sponge also fills up 
all the spaces between the tubes. All three specimens were obtained together, 
and are probably fragments torn away from some large sponge. Neither of 
the three specimens shows any part of the external surface of the sponge, so 
specific identification is impossible. 
The skeleton consists of an irregular reticulation of spicular fibre and 
scattered spicules. In the fibres the spicules vary considerably in number 
and lie somewhat irregularly. The fibres possess from 3 to 8 rows of 
spicules. 
The spicules are oxea, which are frequently slightly curved, and which 
vary tremendously in length, any size up to 0°13 being found. They are 
thickest about the middle of their length, and have a maximum diameter of 
0-005 mm. 
Locality. Not stated. 
Distribution. Red Sea. 
