228 
BULLETIN OP THE UNITED STATES FISH COMMISSION. 
Table showing composition of the shell and gastroliths of the lobster. 
Composition — air dried. 
Carapace. 
Gastroliths. 
i. 
2. 
3. 
4. 
0 a. 
3a. 
4 a. 
11.87 
21.51 
8.48 
9. 12 
1. 37 
3. 96 
Calculated as calcium oxide — CaO 
22. 87 
23.11 
24. 94 
30. 41 
45. 85 
49.14 
50. 82 
Magnesium oxide MgO 
3.18 
1. 14 
1.61 
1.30 
0. 30 
0. 40 
0. 48 
Aluminum oxide — Al 2 O 3 — (Fe 2 0 3 ) 
0.68 
2. 04 
1.04 
1.36 
0. 20 
0. 04 
0. 06 
Sodium oxide — Ha 2 0 
0. 89 
1.06 
1.35 
1.67 
1.09 
1.34 
0. 55 
Silica — Si0 2 
0. 14 
0.29 
0. 08 
0.46 
0. 10 
0. 06 
0. 08 
Phosphoric anhydride — P 2 U 5 
3.53 
3.81 
5. 12 
4.36 
4.43 
4. 16 
5. 12 
Sulphuric anhydride — S0 3 
0. 34 
0.31 
0. 58 
0. 40 
0. 07 
0.08 
0.35 
Carbonic dioxide — C() 2 
Water at 100° C— H 2 0 
21.20 
17. 05 
7. 40 
17. 70 
23. 00 
37. 00 
37. 10 
35. 00 
3. 50 
Calculated as calcium carbonate — CaC0 3 . . 
43.68 
32. 83 
32.93 
44. 60 
72. 44 
78. 87 
78. 46 
Calcium phosphate— Ca 3 (P(>4) 2 
7. 70 
8. 32 
11.18 
9. 52 
9. 67 
9. 08 
11.18 
Calcium sulphate— CaSO-i 
0. 58 
0. 53 
0. 99 
0. G8 
0.12 
0. 14 
0. 59 
Magnesium carbonate — MgC0 3 - 
3. 50 
2. 39 
3.38 
2. 73 
0. 63 
0.84 
1.01 
Sodium carbonate — 3sra,C0 3 
1.51 
1.80 
2.31 
2. 85 
1.87 
2. 28 
0. 93 
Alumina, A1 2 0 3 — (Fe 2 0 3 ) 
0. 68 
2.04 
1.04 
1.36 
0. 20 
0. 04 
0. 06 
Silica — Si0 2 
Organic matter and water, by differ- 
0. 14 
0. 29 
0. 08 
0.46 
0. 10 
0. 06 
0. 08 
ence 
42. 21 
51. 80 
48. 09 
37. 80 
14.97 
8. 69 
7.69 
As will be seen by reference to the table the principal part of the mineral structure 
in the carapace is made np of carbonate of calcium, with some considerable proportion 
of calcium phosphate and of magnesium compounds. The gastroliths differ in being 
much more largely mineral, and in consisting almost entirely of carbonate and phos- 
phate of calcium. All of the specimens contained iron, its quantity being so small 
that it was not thought advisable to make a separation of it from the aluminum. A 
minute proportion of potassium also was present in every case, but its quantity was 
so small that it was detected with difficulty by the spectroscope in the separated 
alkali salts. 
fSTo successful determination of the quantity of chitin in the carapace was attained, 
and no separation of any of the other organic constituents was attempted. The total 
quantity of organic matter and water is reported as the difference between the sum of 
the calculated percentages of inorganic salts and 100. 
The portion of the shell subjected to analysis was taken in each case from the 
carapace, from the part bounded by the cervical groove in front and the branchio- 
cardiac groove above. 
