THE PAUMOTU PLATEAU. 29 



these atolls it was a comparatively simple task to get a fairly good idea 

 of them. We have seen nothing in this more extended examination of the 

 group tending to show that there has anywhere been subsidence. On the 

 contrary, the existing condition of the atolls of the Paumotus cannot, it 

 seems to me, be explained on any other theory except that they have been 

 formed in an area of elevation extending from Matahiva on the west 

 to Pinaki in the east, and from the Gloucester Islands on the south to 

 Tikei on the north, although the islands in the line of Manga Reva to 

 Tahiti are separated from the other Paumotus by a deep channel, nearly 

 200 miles wide and more than 2400 fathoms in depth, with scattered islets 

 and atolls extending from Manga Reva to Pinaki, and northward to Puka- 

 ruha and islands beyond, which are not connected with the extensive plateau 

 upon which the greater number of the Paumotu Islands to the westward of 

 Hao rise. 



The character of the I'eef corals of the Paumotus is very different from 

 that of other coral reef regions I have seen. Nowhere have I seen such a 

 small number of genera, so many small species, and such stunted develop- 

 ment of the corals. The outer reefs in from 3 to 15 fathoms of water are 

 composed almost entirely of dense masses of Astrseans, Pavonia, and of 

 several species of Madrepora and of Pocillipora. 



A yellowish green nodular species of Millepora is very common between 

 the surface and three fathoms. On the shallow reef flats are found the fol- 

 lowing corals arranged in the order of the frequency of their occurrence, — 

 several species of Madrepora, Porites, Goniastrsea, Astrasa, Pocillipora, Alveo- 

 pora, Fungia, Mussa ; no Maeandrinae wei'e found, and, what is specially note- 

 worthy, no huge heads of any of the species of corals mentioned above are 

 to be seen. This is in striking contrast to the colossal masses of so many 

 species of corals which characterize the physiognomy of the Great Barrier 

 Reef of Australia and of the West Indian region. The general absence 

 of the large fleshy Alcyonaria of Australia is very marked in the Paumotus, 

 so far as our experience shows, and there are but few Sponges to be found 

 among the corals. Gorgonians and the like are also infrequent, coming 

 up only in our trawl hauls. Plexaura was found on a shallow reef flat 

 in the lagoon of Makemo, where Allopora is quite common in from 12 to 



