604 WALTER H. BUCHER 
form in residual clays.t The calcareous odlites of Great Salt Lake 
form suspended in the jelly-like masses of algae, as was described 
by Rothpletz.* Drew’s artificial odlites formed in the agar-agar 
of his bacterial culture, and in Vaughan’s experiments they grew 
in the soft amorphous calcareous muds which occur so abundantly 
on the shores of the Bahama Islands. 
Apparent exceptions.—I know of only two cases which at first 
sight at least seem to form exceptions to the rule that odlites grow 
in free suspension. 
1. Gaub, in a splendid paper, described odlites containing 
numerous microscopic shells of a Foraminifer classed with the 
Miliolidae (Ophthalmidium ooliticum).3 ‘These he considers to have 
been incrusting forms which attached themselves to small fragments 
of shells, crinoid stems, etc. (now forming the nucleus of the odlitic 
grains), and, being rolled about in the amorphous calcareous mud, 
held it mechanically and perhaps even localized its precipitation. 
The fact that a very similar, not incrusting, species of the same 
genus Ophthalmidium is very abundant in the same layers suggests — 
the possibility that these minute shells were only mechanically 
inclosed in the growing odlite and that surface tension may be 
responsible for their tangential arrangement. Schade observed, 
for instance, that in some. pearl-like gallstones the holesterin 
crystals were all arranged tangentially, enmeshed in the bind- 
ing colloid. Some of the shells within the odlitic grains are 
flattened on the side facing the center of the odlitic grain. Others, 
however, exhibit similar deficiencies on the outer side. Gaub 
interpreted the former as evidence of attachment, the latter as 
evidence of mechanical wear. They may, however, both be due to 
a small amount of solution during the growth of the odlite. 
C.K. Leith and W. J. Mead, Metamorphic Geology (New York, 1915), pp. 35-37; 
for literature on European ‘“‘bean ores”’ see Beyschlag, Vogt, and Krusch, of. cit., 
P. 990. 
2 A. Rothpletz, “On the Formation of Odlite,” Amer. Geologist, X (1892), 279-82 
(translated from Botanisches Centralblatt, LI [1892], 265-68). 
3 F. Gaub, ‘‘ Die jurassischen Oolite der Schwaebischen Alb,” Geol. und palaeont. 
Abh., N.S., TX (1910), Heft 1. An earlier shorter paper, NV. Jahrb. fiir Min., etc., 
Part IT, (1908), pp. 87-96, Pls. 7-8. 
4 Schade, Kolloidchemische Beihefte, I (1910) 385. 
