192 BULLETIN OF THE BUSSEY INSTITUTION. 
XIX. Shells of Terebratula. Sharples, “ American Journal of Science,” 1871, 
101, 169. 
XX. A Silurian fossil-shell (Zeptena depressa). How, as cited under No. VIII. 
He found also 0.55 % sulphuric acid, and 0.26 % ferric oxide. . 
XXI. Dried sea-shells from the coast at Dunkirk. Boussingault and Payen, 
“ Annales de Chimie et de Physique,” 1842, 6. 463. 
Note to No. XIII. B. of the foregoing Table and List of Authorities. The 
operculum of the garden snail serves only a temporary purpose. In late au- 
‘ tumn, the shell of the snail is closed by means of it, and it remains in place 
during the winter while the snail is buried in the earth. But when the animal 
wakes again in the spring, the operculum is cast off. W. Wicke found, in 
1858 (“ Annalen der Chemie und Pharmacie,” 87. 224), that this operculum 
differed decidedly in composition from the shell proper. According to him, both 
the inner and outer surfaces of the operculum are covered with small warts, 
supposed to consist chiefly of phosphate of lime, which separate in the form of 
little corns when the substance is treated with tolerably concentrated acetic acid, 
and finally dissolve in the acid without effervescence after the whole of the car- 
bonate of-lime has gone into solution. After having treated the operculum with 
warm dilute potash-lye, to remove organic matter, W. Wicke found in it 94.24% 
of carbonate of lime, and 5.73 % of bone phosphate of lime; 7.e., 2.63% of phos- 
phoric acid, beside traces of oxide of iron and magnesia. 
In the operculum of a species of Trochus from the Mediterranean Sea or the 
Indian Ocean, W. Wicke found 98.72% of carbonate of lime, and 1.28% of or- 
ganic matter, and traces of phosphate of magnesia. It will be observed that 
in this case, where the operculum is permanent, and is used during the entire 
life of the animal, it appears not to differ materially in composition from the 
shell proper. 
In the following recent shells, Schlossberger (‘* Annalen der Chemie 
und Pharmacie,’’ 1856, 98. 102) found the stated amounts of carbonic 
acid, from which data he has calculated the corresponding amounts of 
carbonate of lime. The shells appear to have been thoroughly dried be- 
fore being subjected to analysis: — 
COz. Ca0,COrz. CO2. Ca0,COr. 
Venus decussata. . . 41.14 % 93.51 % Cyprzea moneta. . . 40.85 92.85 
Valve of Turborug. . .~-42.48 96.55 Oliva ‘P .. .°. 4. 7400" 0820 
Mytilus edulis (young ex- Turbo neritoides . . 40.69 92.48 
BZVINIES il ce, jas Lash v ope awake 82.12 Turritella fuscata . . 39.02 88.70 
Bulimus radiatus . . . 41.10 93.41 Pupa(W. Indies) . . 41.10 93.48 
Volutarustica ... . 40.45 92.10 Anodonta anatina. . 39.15 88.99 
Cypreaerosa. .. . . 41.45 94.21 Helix nemoralis. . . 36.34 82.62 
Cypreachinensis . . . 41.86 95.16 
In seven different species of corals from the American coast, Sharples * 
found from 0.12 to 0.399% of phosphoric acid, from 1.64 to 3.79% of 
water plus organic matter, and from 95.37 to 98.07% of carbonate of 
lime. For other estimations of the amount of phosphorie acid and the 
other constituents in coral, see Silliman’s paper in ‘‘ American Journal of 
Science’? (2), 1. 189, and Damour, Liebig and Kopp’s ‘‘ Jahresbericht 
der Chemie,’’ 1850, 3. 812, and 1851, 4, 865. 
* “ American Journal of Science,’”” $871, 101. 168. 
