68 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
dried, Canada balsam, somewhat diluted with ether, is poured upon it, 
and the cover-glass adjusted. 
The works of Gustav Rose ' and of Dr. H. C. Sorby ? have dealt largely 
with the mineralogical constitution of various organisms, and to these 
papers, especially that of Dr. Sorby, I am indebted for many helpful 
suggestions. 
One of the results of their researches went to show that the mineral 
composition of most of the reef-forming corals is aragonite. This view 
remained practically unquestioned till 1900, when Miss Agnes Kelly’s 
paper ® appeared ‘‘On a new form of calcium carbonate,” to which she 
gave the name of conchite. The skeletons of the organisms which have 
hitherto been described as being aragonite are claimed by Miss Kelly 
to consist in reality of conchite. It is said to differ from aragonite in its 
uniaxial character and the lower temperature at which it passes over 
into calcite and to have a refractive index intermediate between those 
of calcite and aragonite. 
Quite recently, however, Reinhard Brauns,‘ in a paper on the relation 
of conchite to aragonite, states that while there appear to be certain 
differences, at present there is not positive evidence sufficient to warrant 
the making of a new mineral species. 
Another paper on ktypeite and conchite, by Henrich Vater,® has 
recently appeared, in which he agrees with R. Brauns in saying that 
conchite is probably identical with aragonite. 
As the question is still in doubt, I have used only the term aragonite 
for all material which stains with cobalt nitrate, but if Miss Kelly 
should eventually be proved to be correct in her contention, those 
crystals which are in optical continuity with coral fibers would have to 
be known as conchite. 
The details of the chemical and microscopical analyses from each 
island will now be given. It is to be noted that gravimetric analyses 
are recorded to two places of decimals, while the results of volumetric 
determinations are given only to the first decimal place. 
A certain number only of the limestones have been sliced, and the 
details of their structure and composition are given below. In the de- 
scriptions of the thin sections under the microscope the term ‘“ mud” is 
1 Abh. K. Akad. d. Wiss. in Berlin, 1858. 
2 Pres. Address to Geol. Soc., 1879. 
8 Bay. Academy, May, 1900, and Min. Mag., June, 1900. 
4 Centralblatt fiir Mineralogie, 1901, pp. 184-1865. 
5 Zeitschrift fiir Krystallographie und Mineralogie, 1901, Vol. XXXV., p. 149. 
