66 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
crystals and the coral fibers, some other critical test was desirable in 
order to distinguish between calcite and aragonite. 
Such a method has been described recently by W. Meigen.? 
The method consists in boiling the powdered substance for a few 
minutes in a solution of commercial cobalt nitrate, when a lilac-red 
precipitate of basic carbonate of cobalt indicates the presence of ara- 
gonite, while calcite remains unaffected, or in the presence of organic 
matter becomes yellowish. Barium and strontium, but not magnesium 
carbonates, give the same result as aragonite, while calcium phosphate 
produces a blue precipitate. 
By means of this reaction Meigen distinguished aragonite from calcite 
in various animal and vegetable secretions of calcium carbonate. 
A few of the results of his determinations are here enumerated : 
Aragonite Organisms : — 
CatcarEous ALGc& — Halimeda. 
Corats — Heliopora, Montipora, Madrepora, Millepora, Goniastrea, 
Podobacia, Galaxea, Fungia, Porites, ete. 
LAMELLIBRANCHS — Pholas, Cardium, Lucina, Mya, Cytheraea Unio 
(inner layer of shell), Trigonia (inner layer of shell). 
Gastropops — Helix, Pupa, Bulimus, Cyclostoma, Natica. 
CrpHaLopops — Nautilus, Spirula, Sepia. 
Caleite Organisms : — 
CatcarRzous Anew — Lithophyllum, Lithothamnion. 
Corats — Isis, Tubipora, Cystiphyllum, Anabacia. 
ForAMINIFERA — Polytrema, Nummulites. 
Worms — Serpula. 
EcHINODERMS. 
Meigen’s method was tested by me in the following way, and found to 
give satisfactory results : — 
First, the pure minerals, calcite and aragonite, were treated separately, 
both powdered and in crystals. In each case the calcite was qnite un- 
affected after long boiling, while the pink stain on the aragonite was 
deeper in the powder than ona crystal surface. A coral sand contain- 
ing gastropods, echinid spines, and Foraminifera was next treated, and 
it was found that the gastropods stained deeply, but the echinid spines 
and Foraminifera were unaffected. A polished slice of a limestone was 
taken and boiled for half an hour with cobalt nitrate solution. The 
limestone consisted of coral fragments, gastropods, echinid spines, 
1 Centralblatt fiir Mineralogie, 1901, pp. 577-578. 
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a) Veteeii. . 
