180 BULLETIN OF THE BUSSEY INSTITUTION. 
@ 110°, contained 1.5665 % of magnesia; or, when taken in the air- 
dried state, it contained 1.497%. The oyster-shell contained 0.2779 4, 
of magnesia, when dried at 105° @ 110°, or 0.266% when air-dried. 
The clam-shell contained 0.0329% of magnesia when dried at 105° 
@ 110°, or 0.0328% when air-dried. 
As regards the magnesia in sea-shells, these results do but re-enforce 
a mass of evidence that had been accumulated by previous observers. 
Schlossberger,* for example, found ‘ barely 0.3. @ 0.50 of magnesia in 
oyster-shells dried at 120°.’? Forchhammer f had previously insisted upon 
the small proportion of magnesia that is found in shells and in most corals 
and in most of the chalks and limestones that have been formed directly 
from such shells and corals. Besides analyzing several chalks and lime- 
stones which contained but little magnesia, he examined a number of 
shells and corals, with the following results. He found in 
Carbonate of magne- Or, magnesia, 
Mgo. 
sia, MgO, CO, 
Terebratula psittacea . . . . 0.4579, 0.218 0% 
Modiolus papuana. . - 0.705 0.336 
Pinna nigra, from the Red is - 1.000 0.476 
Tritonium antiqauum . . . . 0.486 0.231 
Cerithium telescopium . . . . 0.189 0.090 
Nautilus Pompilius . . . . . 0.118 0.058 
Ossa Sepiae..(.0., 0. /iewimhs tela soap Ee 0.191 
Astrea cellulosa.. . . . -.. «;,0.m82 0.259 
Myriazoon truncatum . . . . 0.445 0.212 
Helenopora abrotanoides . . . 0.852 0.168 
Eschara foliacea . . . . . . 0.146 0.070 
Frondipora reticulata . . . . 0.596 0.284 
Corallium nobile . . . . . . 2.182 1.015 
Isis hippuris . . - 6.362 3.028 
Serpula Sp., from Moilitertatiedn 4 7.644 3.640 
Serpula triquetra, from North Sea 4.455 2.121 
Serpula filograna, from North Sea 1.349 0.642 
The first three shells in the foregoing list are bivalve; the next two are 
univalve; nautilus and ossa belong to the class of cephalopods; and the 
others are corals, excepting the last three serpulas, which are sea-worms 
that exude a calcareous secretion to form a long, twisted tube, in which 
the animal resides. 
It will be seen that, excepting Corallium and Isis, among the corals, 
and the worm Serpula, the amount of magnesia in the shells seldom ex- 
' ceeds 0.3%. 
* “ Annalen der Chemie und Pharmacie,” 1856, 98, 101. 
t “Journal fiir praktische Chemie,” 1850, 49. 52. 
