FRYER— FORMATION OF ALDABRA, ETC. 411 



Stylopora, Pocillopora, Seriatopora, Cceloria, Hydnopora, Galaxea, Prionastrea, 

 Acanthastrea, Favia, various Fungida, Dendrophyllia, Madrepora, Montipora, Astreo- 

 pora and Porites. Towards the mouth of the pass itself the corals became stunted and 

 often encrusted with lithothamnia* and finally ceased, with the exception of the hydro- 

 coralline Millepora, which was very abundant in the channels and took on a branching 

 fades. The reef by the side of the pass itself was covered with fragments of coral 

 encrusted with lithothamnia, which appeared to flourish exceedingly in the strong current, 

 to the dirt carried by which was attributed the scarcity of reef corals. 



The Passe Houareau reef in most respects resembled that near Grande Passe, but 

 was small and showed a tendency to block the channel somewhat ; the corals were mainly 

 of a massive type, though Seriatopora, scarce at Grande Passe, was quite common. In 

 the mouth of the pass itself Millepora and lithothamnia were again abundant. Near 

 Passe Johnny is a small and unimportant reef and in the channel itself few corals were 

 noted except Dendrophyllia, which elsewhere seemed to frequent deeper water. 



A large area between Esprit Island and the western channels was scattered diffusely 

 with coral colonies, massive forms being scarce and the prevalent type a Madrepora of 

 a slender, horizontally branching fades. 



The sandy portions of the lagoon were searched at low tide but were disappointing ; 

 various holothurians were very common and no doubt play an important part in 

 triturating and reducing the sand. Amphioxus was absent, but in the sand itself were 

 found a few specimens of an enteropneust which Professor Spengel kindly informs me 

 belong to the genus Spengelia or Willeyia ; various polychsets, molluscs, burrowing 

 echinoderms and gephyreans were also obtained, but on the whole the impression was 

 one of great barrenness and absence of life. 



The swamps were even worse in this respect ; in the mud a small polychset, 

 a glycerid, was common, and a large sipunculid not infrequent. On the surface of the 

 mud a large mollusc with a spiral shell was usually present and a few crabs (Sesarma 

 guadratum, Fabr.) climbed about the roots of the mangroves. At high tide numerous 

 free living forms were naturally washed up the creeks but the endemic swamp fauna 

 was small, a fact which Mr Cyril Crossland tells me he also noted in the swamps near 

 Zanzibar. Boring animals, chiefly sipunculids, were obtained from the rock near the. 

 shore, but they were very scarce as compared with the number found in the rock of 

 the sea cliffs. 



Fish were numerous in the lagoon at high tide : they all appeared to be widely 

 distributed marine, forms which drifted in with the tide, and no endemic species were 

 obtained. 



Further reference to this subject is however unnecessary, as subsequent reports will 

 speak for themselves. 



* Lithothamnia is throughout used collectively for the calcareous algae, often erroneously termed nullipores 

 in coral-reef literature. (Vide Foslie, Trans. Linn. Soc., Ser. 2, Zool. Vol. xii. pp. 177 — 192.) 



