/ 
30 Fretp CotumMBIAN MusEum—GeEotocy, VoL. III. 
poles. When compounded, they assume grotesque and imitative 
forms. The nearest approach to the Salton forms is a double con- 
cretion from Saratoga Springs (Plate XX, Fig. 2). This consists of 
two cones with hemispherical bases. They are similar in form but 
differ in size. The apex of the smaller is united with the base of 
the larger. The length of the specimen is 38 centimeters and its 
greatest diameter 8 centimeters. This may be considered as two 
independent concretions which have grown together, and the larger 
cone alone may be compared with the California specimens. This 
larger cone is as smooth on the surface as the sand which enters into 
its composition will permit. It is slightly curved. There is the usual 
fold-like longitudinal swelling where it has grown faster in one 
direction than another. The cone tapers gradually with no abrupt 
change of curve from the widest portion.to the apex. The relation 
between the specimens from Salton and those from Saratoga Springs 
and the Paris Basin are best brought out in tabular form: 
COMPARISON BETWEEN SAND-CALCITE CONCRETIONS FROM THREE 
LOCALITIES: 


Saratoga and the 
Salton. Paris Basin. 

Roughened with rhombo- 






Surface: hedral points. Never Smooth. Often striated. 
striated... 4 
. Simple. 
Bee Gee Compound. Oblate. Prolate or ovoid. 
ney Pseudo-concentric, 
Elongated Circular section. Flattened section. 
forms. Straight. Curved or wavy. 
Junction of / 
pon eee et Abrupt. Always gradual. 
form. 



Lack of data prevents discussion of the nature or origin of these 
concretions from Salton, California. There is, however, one sugges- 
tion which is called forth by the shape of these objects when they 
are compared with some hitherto unrecorded forms of concretions 
of an entirely different character. The stem of any one of these 
California specimens is very like a stalactite depending from the head. 
In certain sand dunes, notably in the ‘‘ Hoosier Slide’’ of Michigan 
City, Indiana, flat sheet-like bodies of limonite concretion form in 
certain strata of the sand. When these are dug out, numerous small 
stalactites of limonite are found depending from their lower surfaces. 
