GEOCHEMISTRY: CLARKE AND WHEELER 
555 
of organisms contributes to the formation of marine limestones, an 
extended study of their organic matter would be hardly relevant. 
If, now, we arrange the alcyonaria in the order of ascending magne- 
sium carbonate, a remarkable relation appears connecting composition 
with the temperature of the habitat. Heliopora, being anomalous, is 
not included in the table. Alycyonium is also excluded, on account of 
its impurities. The percentages of MgCOa and Ca3P208 are both given. 
Magnesium carbonate and calcium phosphate in alcyonaria. 
SPECIES 
LOCALITY 
LATITUDE 
CasPzOs 
MgCOa 
Nova Scotia 
42° 16' N. 
0.83 
6.18 
Lepidisis caryophyllia 
Off Nantucket 
48° 53' N. 
trace 
6.92 
Pennatula aculeata 
Nova Scotia 
44° 47' N. 
3.12 
7.71 
Grand Banks 
1 .43 
8.03 
Nova Scotia 
0.56 
9.05 
Corallium elatior 
Japan 
33° N. 
0.40 
11.56 
Tubipora purpurea 
Singapore 
1° 20' N. 
trace 
12.23 
Muricea echinata 
C. San Lucas 
22° 52' N. 
0.83 
12.28 
Bahamas 
25° 5'N. 
3.64 
12.52 
Muricea humilis 
Brazil 
7°-8° S. 
0.59 
12.64 
Rhipidogorgia flabellum 
Bermuda 
32° N. 
1.09 
12.64 
Xiphogorgia anceps 
Florida 
22° 30' N. 
1.96 
13.04 
Rhipidogorgia flabellum 
Bahamaas 
25° N. 
2.80 
13.19 
Gorgonia acerosa 
Florida 
22° 30' N. 
2.87 
13.29 
Gorgonia suffruticosa 
Fiji 
0.47 
13.43 
L. California 
24° 16' N. 
8.27 
13.71 
Plexaurella grandiflora 
Brazil 
trace 
13.79 
Leptogorgia rigida 
C. San Lucas 
22° 52' N. 
7.95 
14.13 
Torres Straits 
10° S. 
0.88 
15.65 
Phyllogorgia quercifolia 
Brazil 
3° 50' S. 
8.57 
15.73 
Although records of temperature and depth of water are available for 
only a few of these alcyonaria, the suggested relation is clear. The 
organisms from cold, northern waters, or from very deep waters, are 
low in magnesia, while those from warm regions are much higher. The 
same relation appears in our analyses of echinoderms, and is unmis- 
takable; even though it is as yet unexplained. It is not rigorously exact; 
but some apparent irregularities are due to the disturbing effect of 
impurities, such as sand or mud, which appear in the analyses as silica 
and sesquioxides. If these were rejected the percentage of magnesia 
would be raised. Variations are also to be expected because of cold 
or warm currents, and differing depths of water. Very deep water, 
even under the equator, is always cold; while shallow bays, even quite 
far north, may be relatively warm. Possibly also, the alcyonaria may 
form several distinct series, not perfectly comparable as regards chemical 
