REPORT ON THE MONAXONIDA. 119 



lophon chelifer, Ridley and Dendy (PI. XVI. fig. 3 ; PI. XVII. figs. 1, 3, 8). 



1886. lophon chelifer, Ridley and Dendy, Ann. and Mag. Nat. Hist., ser. 5, vol. sviii. p. 349. 



Sponge (PI. XVI. fig. 3) amorphous/ massive, honeycombed. Colour in spirit 

 light brown to black. Texture soft, crumljling. Surface smooth. 



Skeleton. — Composed of an irregular, loose reticulation of spined stylote spicules ; the 

 meshes of the network are more or less rectangular, so that there are two main lines of 

 spicules distinguishable, though only roughly, one of which is approximately perpen- 

 dicular to the surface. 



Spicules. — (rt) Megasclera; (1) spined styli (PI. XVII. fig. 1, a, h), measuring 0'36 

 to 0"42 by 0'016 to 0"02 mm.; (2) there are also present a few tylote spicules (PI. XVII. 

 fig. 1, c), apparently confined to the surface, size 0'25 to 0*32 by 0"01 mm.; these spicules 

 have the shaft smooth and the knobbed extremities minutely spined. (b) Microsclera ; 

 very abundant, of two kinds ; (1) anisochelse (PI. XVII. fig. 8), from 0*019 to 0'03 

 mm. long ; (2) bipocilli (PI. XVII. fig. 3), large (0*019 mm. long) and of very peculiar 

 form ; shaft narrow and strongly bent, small end clawed, with two prongs (whence the 

 specific name), large end bearing two, tliree, or (very rarely) four expanded fiukes, 

 which together form a hollow cup. These spicules occur lining the canals ; the large 

 end is embedded in the wall of the canal, and the small, clawed end projects freely into 

 its lumen.- They also occur scattered abundantly through the soft tissues (perhaps 

 owing to displacement ?). This spicule is the most interesting feature about the species ; 

 it throws considerable light on the relations of the more minute bipocUlate sj^icules of 

 other sponges. We are inclined to regard it as a much modified anisochela; its 

 variability in form (i.e., in the number of flukes forming the larger end of the spicule) 

 is also noteworthy. 



Three specimens of this interesting species are present, two are fairly large, but broken 

 into fragments, the other is small, and occurs encrusting a branched Polyzoon. The 

 latter is in all probability a young form, and differs in several minor respects from the 

 larger specimens ; in it the anisochelse are mainly arranged in rosettes, with the 

 small ends iu the centre, they are very abundant, while, on the other hand, the bipocil- 

 late spicules are very few and apparently imperfectly developed. The species differs 

 very decidedly from all described forms in the large size and also in the degree of 



1 Exact form uncertain, specimen fragmentary. 



- This arrangement would seem to be connected with the protection of the walls of the canals, probably from animal 

 intruders, rendering the spicules truly defensive, a term which cannot be applied to aU the spicules thus named by 

 Bowerbank. The cases in which a spicule may reasonably be assimied to fulfil this purpose are very few, that of the 

 diancistra or "trenchant bihamates" (see Bk., Mon. Brit. Spong., vol. i. p. 34) being perhaps the best established case 

 hitherto recorded. Cf. also the sigmata in Esperella murrayi, nobis. 



