228 



BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Table showing composition of the shell and gastroliths of the lobster. 



Composition— air dried. 



Weight in grams 



Calculated as calcium oxide — CaO 



Magnesium oxide— MgO 



Aluminum oxide — Al 2 O3 — (Fe. 2 3 ) 



Sodi um oxide — N a 2 



Silica— Si0 2 



Phosphoric anhydride — P 2 5 



Sulphuric anhy dride — S0 3 



Carbonic dioxide — C0 2 



Water at 100° C— H 2 



Calculated as calcium carbonate — CaC0 3 . - 



Calcium phosphate— Ca 3 (P04) 2 



Calcium sulphate— CaSOj 



Magnesium carbonate — MgC0 3 



Sodium carbonate — Na 2 C0 3 



Alumina, A1 2 3 - (Fe 2 3 ) 



Silica— Si0 2 



Organic matter and water, by differ- 

 ence 



Carapace. 



11.87 

 22.87 

 3.18 

 0.68 

 0.89 

 0.14 

 3.53 

 0.34 

 21.20 



43.68 

 7.70 

 0.58 

 3.50 

 1.51 

 0.68 

 0.14 



42.21 



21.51 



23.11 

 1.14 

 2.04 

 1.06 

 0.29 

 3.81 

 0.31 



17.05 

 7.40 



32.83 

 8.32 

 0.53 

 2.39 

 1.80 

 2.04 

 0.29 



51.80 



8.48 

 24.94 

 1.61 

 1.04 

 1.35 

 0.08 

 5.12 

 0.58 

 17.70 



32.93 

 11.18 

 0.99 

 3.38 

 2.31 

 1.04 

 0.08 



48.09 



9.12 

 30.41 

 1.30 

 1.36 

 1.67 

 0.46 

 4.36 

 0.40 

 23.00 



44.60 

 9.52 

 0. 68 

 2.73 

 2.85 

 1.36 

 0.46 



37.80 



Gastroliths. 



0a. 



1.37 

 45.85 

 0.30 

 0.20 

 1.09 

 0.10 

 4.43 

 0.07 

 37.00 



72.44 

 9.67 

 0.12 

 0.63 

 1.87 

 0.20 

 0.10 



14.97 



3d. 



49.14 

 0.40 

 0.04 

 1.34 

 0.06 

 4.16 

 0.08 



37.10 



78.87 

 9.08 

 0.14 

 0.84 

 2.28 

 0.04 

 0.06 



8.69 



4a. 



3.96 



50.82 



0.48 



0.06 



0.55 



0.08 



5.12 



0.35 



35. 00 



3.50 



78.46 



11.18 



0.59 



1.01 



0.93 



0.06 



0.08 



As will be seen by reference to the table the principal part of the mineral structure 

 in the carapace is made up of carbonate of calcium, with some considerable proportion 

 of calcium phosphate and of magnesium compounds. The gastroliths differ in being 

 mucb 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. 



No 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. 



