GEOCHEMISTRY: CLARKE AND WHEELER 
265 
Phosphatic hrachiopods 
12 3 4 
SiOa 0.91 0.50 0.85 0.49 
(Al,Fe)203 0.54 0.29 0.58 1.16 
MgCOa 2.70 0.79 6.68 1.71 
CaCOs 1.18 4.25 8.35 ? 
CaS04 . 2.93 4.18 8.37 ? 
CaaPaOs ^^^.i^ 89.99 75.17 74.73 
100.00 100.00 100.00 
These analyses are noteworthy, on account of the unusual proportion 
of calcium sulphate reported in them. Discinisca is especially remarka- 
ble in this respect, and also in its percentage of magnesium carbonate. 
Small amounts of sulphates have often been found in mollusks and cor- 
als as well as in the calcareous hrachiopods, but in nothing like the pro- 
portion given here. A new analysis of Discinisca, made upon fresh ma- 
terial, is much to be desired. 
In the older analyses of this group 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 ovalis. LocaHty not given. A. Hilger, analyst.^ 
8. Lingula anatina. S. Cloez, analyst.^ Recalculated to 100% after 
rejecting 42.6% of organic matter. 
Older analyses of phosphatic hrachiopods 
5 6 7 8 
SiOa 0.18 0.17 trace 
MgCOa 2.94 3.13 
CaCOs 11.75 10.76 10.86 12.19 
CaaPaOg 85.79 84.94 85.24 77.17 
MggPaOs .... .... 7.03 
FeP04 0.77 0.76 3.61 
MgO(?) 2.80 
100.34 99.59 100.16 100.00 
In this table the relatively high figures for CaCOa are doubtless due 
to the neglect of the sulphate determinations. The analysis by Cloez 
differs from the others principally in form, that is, in its mode of calcu- 
lation. If the phosphoric oxide in it is entirely assigned to the lime, 
then the proportion of calcium phosphate becomes 88.6%, and well in 
line with the other figures. The amount of calcium carbonate would 
be correspondingly reduced. 
Now to sum up. The hrachiopods, as stated at the beginning of this 
paper, are to be divided into two distinct groups; the shells of one con- 
sisting mainly of calcium carbonate with little organic matter; and of 
