Plate III. Photograph of fossil casts of a close tangle of ice crystals
seen in a stony calcareous layer in the Eagle Ford shale in Walnut
Creek, about eight miles north of Austin, Texas. This tangle is closer
than any of the recent ice crystal marks figured here, but equally
closely grown crystals have been seen by the writer on frozen mud in
Illinois. Natural size. Compare with Plate VIII.
[Illustration: PLATE III]