I905.J CAPE VEKDE' Sr'AElNB FAUNA.. 1'8I 



also during the life of the animal, but Pecten remains free. The 

 upper coils of Gastropoda are generally bored, but a large white 

 Muyex escapes. The sponge seems to have a selective action in the 

 case of living organisms — e. g., a dead oyster-shell was dredged 

 which had been riddled with sponge : on one side was growing 

 nullipore and on the other a thick soft crust of Polyzoa, both of 

 which were free. 



The small irregular cavities enclosed by the growth of encrusting 

 species of nullipore are a great aid to the spread of the sponge 

 through the mass. The more solid Astrpeid Corals are far less 

 rapidly attacked. Hemispherical lumps, apparently long dead, are 

 frequently dredged, which are quite white and clean inside except 

 for a tinge of red near the surface, or one or two layers of the 

 same concentric with this. Some of these lumps have as nuclei a 

 nullipore nodule, which is absolutely rotten. 



(2) Polychceta. — Lysidice, Nicidion, two species of Sabellidfe, 

 Dodecaceria concharum and Eimice siciliensis are ubiquitous in the 

 same places and geneiuUy in company with the sponge. Of these 

 the Eunicidfe are the most important, but the one large species, 

 E. siciliensis, the great borer of the Indo-Pacific Corals, is lare. 

 The Sabellidfe, which are not so conspicuous as borers in East 

 Africa, here occupy an important place. Dodecaceria, the well- 

 known shell-borer of European seas, here occupies a subordinate 

 position. Wherever found it occurs in numbers together, but it 

 does not occur with anything like the frequency of the Eunicidfe 

 and Sabellidfe. A favourite habitat for this and other species is the 

 base of coral-colonies. Splitting an encrusting Astrfeid fi'om the 

 lava rock usually lays bare a number of galleries and their 

 occupants. The small Eunicid?e Lysidice and Niddion are 

 especially characteristic borers of the encrusting nullijDore of 

 exposed positions, the Sabellidfe of dredged Lithothamnion nodules, 

 bvit either may occur in any position. Although in all cases 

 sponge seems to be the first of the attacking host, yet in the case 

 of the Astrfeid Corals, whose pores are too minute for the purjDose, 

 the rapid spread of the sponge is dependent on the presence of 

 unoccupied worm-burrows, around which are seen extensions of 

 the red tint from the surface, or other zones, into the white and as 

 yet unattacked portions of the mass. The final state of a nullipore 

 nodule is a grey mud enclosed in a thin shell of still growing Alga. 

 The Sponge and boring Polychpeta have now disappeared, the sole 

 inhabitant being a. large but remarkably fragile Capitellid worm. 



(3) The Lamellibranch Litliophagiis is abundant in Corals; 

 nulli pores are nearly always infested and very often are quite full 

 of it. This species is notable as being the only borer to attack the 

 Serpulid and nullipore compound when the proportion of the latter 

 is low. 



Lithophagus lines its bvirrows with a hard enamel-like secretion 

 which is not attacked by sponge until after the death of the mollusc. 



(4) SipuMCuloidea : Aspidosiphon is common in both nullipore 

 and Coral. 



