SKEATS : CHEMICAL COMPOSITION OF LIMESTONES. 85 
comprise coral fragments, Polytrema, Lithothamnion, and much-altered 
Halimeda. 
350’. Similar to the rock from 360 feet, except that the concentric 
coating to the fragments is rather less prominent. 
310’. Consists of Polytrema, coral fragments, Lithothamnion, Gyp- 
sina, etc., with a feebly marked concentric coating of fibrous calcite. 
140’. First Terrace. — Gypsina and Carpenteria can be recognized, but 
all the aragonite organisms, including the corals, have recrystallized to 
clear calcite. The matrix consists mostly of “mud,” and no fibrous 
calcite surrounds the organisms. 
D. The Paumotus Group. 
The islands of this group are described by Mr. Agassiz, in connection 
with the explorations of the “ Albatross.”! He finds that the western 
part of the Paumotus consists of a partly submerged ledge of older coral- 
liferous limestone covered with a thin modern reef. The land of the 
Paumotus atolls is built up simultaneously by accumulations of sand 
both from the lagoon side and also from the sea face. Mr. Agassiz 
regards this circumstance as characteristic of the group. 
Maxatea (called also Mehetia, Metia, or Aurora Island) is situated in 
latitude 17° 45’ S., longitude 148° 3/ W., and consists of upraised coral- 
liferous limestone. The greatest elevation is 230 feet, and a central de- 
pression exists 50 feet lower than the rim of either face. At the western 
end of the island four terraces can be traced. 
Chemical. — This island gained geological importance owing to the visit 
of Prof. J. D. Dana, and the fact that the first specimen of dolomi- 
tized coral limestone was collected by him from this locality. The speci- 
mens from the terraces and central basin, which I have analyzed, show, 
however, ‘practically no dolomitization, as the percentage of magnesium 
carbonate in the rocks does not rise above 3.7. This result is interesting 
as illustrating the partial character of the dolomitization which this island, 
in common with many others, has undergone. 
Calcium Magnesium Insoluble 
Height. ' Carbonate. Carbonate. Residue. 
3rd Terrace 96.5 3.5 
=f: 200’ 97.2 2.8 
a 200’ 96.5 3.5 
2nd Terrace 96.5 3.3 .20 
Basin 150’ 96.3 3.7 
1 American Journal of Science, 1900, pp. 34-48; Mem. Mus. Comp. Zodl., 1902, 
Vol. XXVI. No. 1, p. 18. 
