38 



THE INORGANIC CONSTITUENTS OF MARINE INVERTEBRATES. 



These analyses are noteworthy on account of the unusual proportion of calcium sulphate 

 reported in them. Discinisca is especially remarkable in this respect and also in its percentage 

 of magnesium carbonate. .Small amounts of sulphates have been found in many moUusks and 

 corals as well as in the calcareous brachiopods but in nothing like the proportion given here. 

 A new analysis of Discinuca made upon fresh material is much to be desirecl. 



In the older analyses of this gr(nip the sulphate seems to have been ignored, or at least 

 to have escaped attention. The figures are as follows: 



5. Lingula ovalis. Hawaiian Islands; T. S. Hunt, analyst.'^ 



6, 7. Lingula oralis. Locality not given; A. Hilger. analyst.^* 



8. Lingula anatina. S. Cloez, analyst:'^^ recalculated to 100 per cent after rejecting 42.6 per cent of organic matter. 



Older analyses of phosphatic brachiopods. 



The relatively high figures for calcium carbonate shown in this table are doubtless due to 

 the neglect to determine sulphate. The analysis by Cloez differs from the others principally in 

 form — that is, in its mode of calculation. If the phosphoric oxide in it is assigned entirely to 

 the lime, then the proportion of calcium phosphate becomes 88.6 per cent, which is well in line 

 with the other figures. The amount of calcium carbonate would be correspondingly reduced. 



The brachiopods, as stated at the beginning of this section, fall into two distinct groups; 

 the shells of one consist mainly of calcium carbonate, with little organic matter, and those of 

 the other predominatingly of calcium phosphate, with much organic matter. The two groups, 

 although they may be alike structurally, are physiologically quite dissimilar, the chemical 

 reactions involved in building the shells being of two different orders. Such a distinction 

 ouglit to be significant to biologists, and it is for them to determine what it means. Geologically, 

 however, we can see that the phosphatic brachiopods have probably played some part in the 

 formation of phosphatic sediments, a function which is shared by vertebrate animals and some 

 crustaceans. 



MOLLUSKS. 



Numerous analyses of molluscan shells have been published, and tiiey show remarkable 

 uniformity of composition. It has nevertheless seemed desirable to make a liberal series of 

 new analyses, which arc best classified into groups. Sulphates were not determined, except 

 in four analyses. 



1. PELECYPODS. 



The pelecypod shells analyzed arc as follows : 



1. Astarte crenala Gray. Off Marthas Vineyard, Mass.; depth of water, 608 meters; bottom temperature, 7.2° C. 

 2 Callista convexa Say. Vineyard Sound, Mass. 



3. Macoma sabulosa Spengler. Massachusetts Bay; depth, 825 meters; bottom temperature, 5.5° C. 



4. Pecten dislocatus Say. Charlotte Harbor, Fla. 



5. Pecten venlricosus Sowerby. Head of Concepcion Bay. Lower California. 



6. Venericardia ventricosa Gould. Off Point Conception, southern California; latitude, 34° 25' N.: depth, 447 

 meters; bottom temperature. 7.3° C. 



7. Cardiuni substriahim Coniad. Long Reach, Calif. 



8. Calyplogena pacifica DalL Clarence Strait. Alaska; latitude, 55° 46' N.; depth, 589 meters; bottom tempera- 

 ture, 5.8° C. 



9. Nucula expanser Hancock. North of Bering Strait. 



10. Acila mirabilis Adams and Reeve. Japan Sea, off the coast of Chosen (Korea); depth, 128 meters; bottom 

 temperature, 16° C. 



11. Placuna orbicularis Retzius. Off Luzon, Philippine Islands. 



» Logan, VV. E., and Hunt. T. S,. Am. Jour. Sci., 2d ser., vol. 17, p. 2.17, 18.54. 



'< Hilger, A., Jour, prakt. Chemic, vol. 102, p. 418, 1867. 



'■' Cloez. S.. Jahresb. Chemie, 18.59, p. 642; from L'Institut, 1859, p. 240. 



