316 



J. STANLEY GARDINER. 



Even where the reef lies against the open sea, it is freely studded between 10 and 15 

 fathoms with species of nearly all the massive genera of corals, forming rounded colonies 

 up to a few feet in diameter, often dead in the centre. The branching genera are not 

 perhaps as numerous ; where they occur the facies of their growth is that of low spreading 

 thickets with very occasionally a larger tree of some vigorously growing species of Madrepora 

 or Pocillopora, casting defiance at all law and reaching to within 3 or 4 fathoms of the 

 surface. The reef in the above-mentioned, protected situations in many places appears to 

 be almost completely covered with growing corals, which interlock, strive and struggle with 

 one another in the same way and quite as much as, or even more than, on the most 

 luxuriant lagoon reef in the whole groups 



Lithoth amnion may appear almost non-existent in a surface view, but on all outer slopes 

 at this depth (10 to 15 fathoms), wherever a bare space is to be seen, — not a pit overhung 

 by corals — there at the least a thin coating of the incrusting species of this organism will 

 certainly be found. Sometimes the forms of the genus seem to grow into rounded or nodular 

 masses, 2 to 3 feet or more in diameter, and standing up on the basal rock, but all such 

 that I have examined have a basis — a central nodule — formed by some coral or other 

 organism, which they have overgrown and perchance killed. Even in small masses of less 

 than a foot in diameter a thickness for the nullipore of 2 to 3 inches is not unusual. In 

 reality nearly everywhere these calcareous plants are growing at the bases of the corals. 

 The coral colonies are ordinarily dominant, but, when one becomes sickly, the species of 

 Lithothamnion soon claim sway, and extinguish it. In addition small, coarsely or finely 

 branching growths of the same genus are also found, but these facies are of little importance 

 as reef builders. Indeed the main significance of Lithothamnion lies in the peculiar mode 

 of growth of its incrusting species. Whatever is reclaimed from the sea by any coral 

 organism is secured by these plants, and firmly anchored once for all time to the reef so 

 far as the action of the external ocean is concerned. 



Dredging on the outer reefs is such uncertain work even in a steamer — and in addition 

 so dangerous in a sailing vessel as to be almost impossible — that we could not afford the 

 time necessary to make a proper study of the organisms below the depth of 15 fathoms, 

 above which we could see what we were doing. Such organisms, as we secured from it, 

 were only obtained while attempting to ascertain its general topography, of which I have 

 already given a sufficiently full account. 



' It is quite impossible to collect and investigate an area 

 such as this without extremely calm weather, tackle of the 

 strongest description, and most important a steamship. 



A Priestman's grab, such as can be used by hand, seldom 

 secures a coral of any massive genus and only broken stems 

 of branching genera. The smaller massive colonies spread 

 outwards at their attached bases, and the grab cannot be 

 fixed on them. Moreover there is always some roll of the 

 sea even in the calmest weather, and, when a coral mass of 

 even 8 or 10 inches in breadth is securely fixed in the grab, a 

 whaleboat or small launch will be pulled under the approach- 

 ing waves before it be released. 



The genera of the corals from to 5 fathoms, forming 

 only small colonies and the zone being difficult to examine, 

 could not be accurately determined. Finely branching species 

 of Pocillopora were, however, evidently by far the most 



abundant. 



The following is a complete list of coral genera observed 

 from 5 to 1.5 fathoms outside the reefs, the first 10 arranged 

 in the order of their importance as builders in this position : 



Leptoria. 



