3. Shells of hens' eggs contain approximately 97 per cent. CaCO3, 1 per cent. Ca3(PO4)2, including some small quantities of magnesium phosphate and carbonate, and also 2 per cent, of organic matter. (Bronn: Klassen und Ordnung des Thierreiches, 1891, vi4, 875). This carbonate probably exists in the form of calcit. (Kelly, Agnes: Beitr\l=a"\ge zur mineralogischer Kentniss der Kalkausscheidung im Tierreiche, Jenaische Ztschr. f. Naturwissensch., 1901, new series, xxviii, 439.