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APPENDIX. 
shore, and there are spaces within them, not opposite to 
any valley, from 10 to 15 fathoms deep. According to a 
MS. chart of the group by Lieut. Elmer in the Admiralty, 
there is a large space within the reef with deepish water : 
although the high land does not hold a central position 
with respect to the reefs, as is generally the case, I have 
little doubt that the reefs of the Pelew Islands ought to be 
ranked in the harrier class, and I have coloured them pale 
blue. In Lieut. Elmer’s chart there is a horse-shoe-formed 
shoal, 13 miles N.W. of Pelew, with 15 fathoms within the 
reef, and some dry banks on it ; coloured dark blue. — 
Spanish, Martires, Sanserot, Pulo Anna and Maricre 
Islands are not coloured, because I know nothing about 
them, excepting that according to Krusenstern, the second, 
third, and fourth mentioned, are low, placed on coral-reefs, 
and therefore perhaps include a lagoon ; but Pulo Mariere is 
a little higher. Since the above remarks were written Prof. 
Semper has published an interesting article (Zeitschr. f. 
Wissensch. Zoologie, Bd. xiii. 1863, p. 558) on these 
islands. He states that the southern islands consist of 
coral-rock, upraised to the height of from 400 to 500 feet ; 
and some of them, before their upheaval, seem to have ex- 
isted as atolls. They are now merely fringed by living reefs. 
The northern islands are volcanic, deeply indented by bays, 
and are fronted by barrier-reefs. To the north there are 
three true atolls. Prof. Semper doubts whether the whole 
group has subsided, partly from the fact of the southern 
islands being formed of upraised coral-rock ; but there seems 
to me no improbability in their having originally subsided, 
then having been upraised (probably at the time when the 
volcanic rocks to the north were erupted), and again having 
subsided. The existence of atolls and barrier-reefs in close 
proximity is manifestly not opposed to my views. On the 
other hand, the presence of reefs fringing the southern 
islands is opposed to my views, as such reefs generally indi- 
