JUNE, 1906. New Forms oF ConcRETIONS—NICHOLS. cys 
appear unprofitable until their occurrence has been investigated in 
the field. 
EIMONITE GEODES FROM THE OHIO RIVER 

A series of four hollow limonite objects (Museum No. G. 1307) 
of rhombohedral form which were presented to the Museum by Dr. 
W.8S. Gilmore prove to be limonite geodes. (Plate XXIV, Figs 1 
and 2.) They are described as occurring in large numbers in clay 
upon the banks of the Ohio River about 30 miles from Owensboro, Ky. 
They are small, weighing from 28 to 64 grams. They are all of 
approximately the same’ thickness, 25 millimeters, the same width, 
2s millimeters and vary in length from 26 to 60 millimeters. With 
the exception of one imperfect specimen they are bounded by plane 
faces and are in form typical joint rhombohedrons formed between 
bedding planes and three systems of parallel and intersecting joints 
perpendicular to the bedding. Two systems of the joints are practi- 
cally perpendicular to each other. The third system intersects the 
others at angles varying from 40° to 60°. In all the specimens two 
parallel surfaces which differ in color from, and are more earthy in 
texture and rougher than the others, are identified as bedding planes. 
The surface of the geodes is yellow on the bedding planes 
and dull red to brown on the joint faces. Fractured surfaces are 
dull brown and smooth, with a yellow streak at the inside edge. The 
specimens are hollow, with thicker walls along the bedding planes 
than along the joint surfaces. 
In one specimen (Plate XXIV, Fig. 2) the walls of the geode in 
contact with the bedding planes have a thickness of 5 to 7 millimeters, 
while the walls in contact with joint planes have a thickness of only 1 to 
2 millimeters. This specimen happens to be double, the half-specimen 
or individual to which the above measurements refer having a breadth 
and thickness respectively of 24 and 16 millimeters. The interior 
hollows of the unbroken geodes are filled with a tough, yellow, och- 
reous clay, reticulated on the surface with drying cracks. 
It is very ev dent from the form and structure of these objects 
that they are formed at the intersection of joints and bedding planes. 
They do not represent actual open spaces, but rather are blocks of 
clay enclosed by these fractures and modified by the introduction of 
limonite from the exterior by ferruginous waters. These waters do 
not appear to have deposited their iron in the joint openings them- 
