134 MR. A. E. FINCKH. 



lichenoiis form ; (6) the thinly branching species ; (c) the lichenous variety characterised 

 by its stony knobs.* 



(a) The lichenous form is exceedingly common. It is found on the lagoon platform 

 and on the ocean face of the entire rim, as well as on all the shoals. Its upper limit 

 of growth is approximately that of low- water spring tides, or as far as the Avaves 

 usually wash at this level. It is easily recognised down to 3 to 4 fathoms, but beyond 

 that depth it loses its characteristic colour, and being thus obscured its presence 

 cannot be detected with certainty ])y means of the water telescope. It is, however, 

 indubitable that a lichenous or encrusting type of Lithothamnion flourishes on the 

 submarine slope of the atoll even down to depths of 200 fathoms. This was proved 

 by the evidence afforded by fragments broken off in situ by the chisel down to such 

 depths and then caught in the tangles and brought to the surface during the dredging 

 operations carried on both during the 1897 and 1898 Expeditions. 



{h) The second variety, the thinly branching form, is exclusively confined to the 

 western, i.e., the leeward rim. There it grows very abundantly on the surface of 

 the ocean and lagoon platforms, its upper limit being, as in the case of the other 

 forms, that of low-water spring tides. On the ocean walls of the platforms it was 

 not observed to occur more than a foot or two below low water ; in the lagoon, 

 however, large areas were noticed in 2 to 3 fathoms of water. It was never obtained 

 alive during dredging operations in the lagoon, which were carried on from 8 to 26 

 fathoms, so that bathymetrically it seems to have a very limited range, whereas 

 geographically its distribution is now limited to the western rim. 



(c) The third species of Lithothamnion is tlie liclienous form witli its stony knobs. 

 This variety was also found to be totally absent from the eastern rim, although dead 

 fragments were connnon on the sandy beach near the village. It is very common on 

 the lagoon reef platform between the islets of Mulitefala and Fualifeke and on the 

 shoals lying off it. Again, it is met in association with the thinly branching form 

 on the western rim of the atoll. Its bathymetrical distribution seems to be the same 

 as that of the thinly-branching form. 



During the ocean dredgings, loose cakes and flat pieces of calcareous rock up to 

 1 foot in diameter and abo\it an inch in thickness were frequently l:»rought up from 

 considerable depths, some from over 90 fathoms. These were covered with various 

 encrusting organisms which are certainly TAthotliamnion, but it will require 

 microscopical examination before their relation to the above three surface species can 

 be determined. 



As already stated, fragments of similar Lithotliainnion were frequently obtained 

 from depths of over 1 00 fathoms iii. situ. That they were in situ is ])roved by the 

 following facts : — (a) The pieces showed fresh fractures which prove that tliey have 

 been detached by the chisel or hemp-tangles, (h) They were associated frequently 

 with various deep-sea corals, such as Neohelia (2), Balanophyllia, &c. 



* See hIso pp. 137, 145, 155, d «■(/. 



