344 A NATURALIST ON THE "CHALLENGER." 



Porites the consequent flattening of the top and expansion of 

 the lateral dimensions was most excellently shown in pieces 

 convenient for museum purposes. 



The Corals, which were few in number of species, were finer 

 grown towards the outer verge of the reef, as is always the case 

 on shore platforms, the very opposite condition to that which 

 holds in case of barrier reefs. In some places were deep holes 

 in the coral platform, reminding one of glacier crevasses on 

 a small scale, evidently arising from the loose nature of the 

 sloping beach on which the coral structure here rests. On the 

 reef rest weathered remains of a more ancient shore platform 

 which are honey-combed and wave-worn. The rock composing 

 them is, however, undoubtedly in situ, and proves elevation of 

 the islands to the extent of five feet or so. Similar fragments 

 of raised reef were found by Mr. Murray at a short distance up 

 the bed of the stream already mentioned. A massive porites was 

 one of the corals on the reef. Some specimens of this species 

 were unattached, though living, being in the form of rounded 

 masses, entirely covered with living polyps, and I suppose from 

 time to time rolled over by the waves. They reminded me of 

 the similarly detached rounded masses formed by some Lichens 

 (Lecanora esculenta), which are rolled about over the land by the 

 winds as are these coral colonies by the waves. 



On the reefs were comparatively few free living animals, but 

 here I saw for the first time one of the huge Synaptas, which are 

 abundant amongst the East Indian Islands and at the Philippines. 

 The animal was a yard long and two inches in diameter, and 

 looked like an ugly brown and black snake. The instant I 

 touched one I knew what it was, for I felt the anchor-shaped 

 hooks in its skin cling to my hand. 



One animal on the reefs I could not understand the nature 

 of. About six white tentacles, each nearly six inches in length, 

 and of a uniform thickness of not more than -^th of an inch, 

 were expanded on the reef in a radiate manner. On irritation 

 they were slowly but entirely retracted. I could not succeed in 

 digging the owner of them out of the reef rock. I have never 

 seen this animal elsewhere. 



Above the shore the first land plant met with is the ubi- 



