DESCRIPTION OF THE PLATES. 7 



Fig. 3. — HOGOLEU, or ROUG, in the Caroline Archipelago ; 

 taken from the Atlas of the Voyage of the Astrolabe^ 

 compiled from the surveys of Captains Duperrey and 

 D'Urville ; the depth of the immense lagoon-like space 

 within the reef is not known. 



Fig. 4. — Raiatea, in the Society Archipelago ; from the map 

 given in the quarto edition of Cootfs First Voyage; it is 

 probably not accurate. 



Fig. 5.— Gambier Islands, in the southern part of the Low 

 Archipelago ; from the survey by Capt. Beechey ; height 

 of highest island, 1,246 feet ; the islands are surrounded by 

 extensive and irregular reefs ; the reef on the southern side 

 is submerged. 



PLATE III. 



Fig. 1. — Maurua, in the Society Archipelago ; from the survey 

 by Capt. Duperrey in the Coquille : height of land about 

 800 feet 



Fig. 2. — Maldiva Archipelago, in the Indian Ocean ; from 

 the survey by Capt. Moresby and Lieut. Powell. 



Fig. 3. — New Caledonia, in the western part of the Pacific; 

 from Krusenstern's At/as, compiled from several sur- 

 veys; I have slightly altered the northern point of the 

 reef, in accordance with the Atlas of the Voyage of the 

 Astrolabe. In Krusenstern's Atlas^ the reef is repre- 

 sented by a single line with crosses ; I have for the sake 

 of uniformity added an interior line. 



Fig. 4.— MAHLOS Mahdoo ATOLL, together with Horsburgh 

 atoll, in the Maldiva Archipelago ; from the survey by 

 Capt. Moresby and Lieut. Powell ; the white spaces 

 in the middle of the separate small reefs, both on the 

 margin and in the middle part, are meant to represent 

 little lagoons; but it was found not possible to distinguish 

 them clearly from the small islets, which have been formed 

 on these same small reefs ; many of the smaller reefs could 



