Plate VII. Photographs of three fragments of flags showing casts 

 of ice crystals on the under side. All observations made on crystals 

 of this kind indicate local differences in the forms of ice crystals 

 presumably due to differences in the rate of freezing, in the texture 

 of the mud and probably in variations in water content of the mud. 

 Some crystals in the locality from which these specimens came, show 

 pinnate secondary growths. Specimens shown here are from near 

 the upper part of the Eagle Ford at a point about two miles north 

 from the Chisos Mining Company's property, Brewster County, Texas. 

 Slightly reduced. 



