6 Universiti/ of Texan Bulletin 



the photographs of the patterns I have photographed from 

 the Eagle Ford, it appears to me that no doubt can be left 

 as to the origin of the markings found in the fossil state. 



Recently I have found that these ice crystal marks are 

 quite common at one horizon in the Eagle Ford beds of 

 Brewster County, in Texas. There is also a layer in which 

 they can be usually seen in the vicinity of Austin, Texas. 

 This lies about twenty-five feet below the Austin Chalk, 

 near Austin. A like layer occurs about 100 feet below the 

 Austin Chalk in the Big Bend country. Here I have found 

 the markings in localities thirty miles apart. They occur 

 at the north point of Mariscal Mountain and in a number 

 of places near the Fossil Knobs and on the Chisos Mining 

 Company property at Terlingua. 



Unprofitable as observations on such a simple matter as 

 this may seem, I find that other geologists have given it 

 some attention. Quite recently, Dr. John M. Clarke* has 

 figured slabs showing what has been described as Fucoides 

 graphica, by Hall. The markings figured by Professor 

 Clarke are undoubtedly of the same kind as those I have 

 found in the Eagle Ford. They occur in the Upper Devonian 

 in New York. I also find that the formation of ice crystals 

 in wet mud has been observed in the clays about Boston 

 by Marbut and Woodworth.** Other observations of simi- 

 lar recent markings are said to have been made by some 

 English geologists. 



To "practical people" it may indeed appear that no more 

 unprofitable or more idle curiosity could be indulged in, 

 than making observations on what kind of crystals are 

 formed when water freezes in mud. I must confess that 

 my own first observations had no motive whatever, except 

 for the desire to know something new ; and I never ex- 

 pected that anything I could learn about these fossil marks 

 would ever turn out to have any practical application, at 

 least not in my own work. 



* Strand and undertow markings, etc., New York State Museum, 

 Bulletin No. 196, April 1, 1917, pp. 199-210; pi. 20-23. 



**Brick clays of Rhode Island, Massachusetts; Marbut and Wood- 

 worth, U. S. Geol. Survey, 17th Ann. Rep., Pt. 1, p. 992. 



