342 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



rock island is found (San Augustin) which rises to a height of 107 feet; 

 on the southeastern end of the atoll a small limestone island. Baxo 

 Trista, is fifty feet high. 



The Seniavina Islands. 



We next visited the Seniavina Islands ; they consist of the liigh volcanic 

 island Ponapi and the low atolls Pakin and Andenia ; tlie last are separated 

 from Ponapi by deep water. Ponapi rises to a height of nearly 2900 feet, 

 while the atolls of Andema and Pakin have been thrown up on a volcanic 

 platform, denuded to about the level of the sea, or upon a summit elevated 

 to the depth at which corals grow. 



Ponapi. 



Plates lSS-190, figs. 1-3 ; 225, 230. 



The island of Ponapi is about twelve miles long north and south and 

 perhaps thirteen miles from east to west. It is surrounded by a wide 

 reef flat ; at some points this is nearly three and one-half miles in width 

 (PI. 230). Within the barrier reef surrounding the main island a number 

 of smaller volcanic islands are formed, satellites as it were of the principal 

 island ; on the outer edge of the reef flat a number of low coral sand 

 islands have been thrown up. 



Ponapi is distinguished .from Kusaie by the number of the volcanic 

 islands enclosed within the barrier reef; their position shows even better 

 than at Kusaie how a wide and broad reef flat has been eroded from 

 the central mass and has left as outliers such islands as Jekoits, Parum, 

 Langa, Mantapeti, Tababac, Tacahu, Mutokaloj, Tauche, Mutok, Tulatik, 

 Tahuak, and other islands, all in the extension of spurs from the main 

 ridge (Pis. 188; 189, figs. 1-3; 190, figs. 1, 2); in some cases they are 

 on the very outer edge of the barrier reef (Pi. 230). 



The base of the volcanic .slopes of Ponapi is, like Kusaie, fringed 



