MARKINGS IN PENNSYLVANIAN SANDSTONES 75 
Short, rodlike markings of obscure origin, so-called Fucoides 
graphica, recently have been ascribed to ice crystals by Dr. Clarke 
at the suggestion of Professor Woodworth.t Dr. Udden has 
enlarged on the suggestion by redescribing similar markings in the 
Cretaceous of Texas and of the Black Hills as fossil ice crystals.? 
The markings resemble the shorter ones on Figure 4. They are 
either straight or curved; they are 1 inch to 2 inches in length 
and 53; to + inch in diameter. The same markings are common 
in the Osage, and in the continuation of the same sandstones near 
Henryetta, Oklahoma. Faint 
markings of the same shape 
occur in the same horizon as 
some of the grooves. Meas- 
ured ice crystals have not ex- 
actly the same shape as most 
of the supposed fossil crystals, 
_ but the branching and radiat- 
“ ing forms are similar. The 
Fic. 7.—Casts of diverging grooves on specimens in the New York 
the lower surfaces of sandstone blocks. State Museum show that the 
The upper figure shows a slab 4 feet long 
in stone wall near Tulsa Country Club, supposed Cy stals represent 
Tulsa, Oklahoma; the lower figure shows casts of crystals or of objects 
a slab 5 feet long at the same locality as partly buried in the mud, be- 
ete cause the ridges in the cast 
where they join or cross are distinctly superimposed, and in one 
case the newer object has bent down the older one. Ice crystals 
could scarcely bend one another, nor could they be depressed by 
any objects moving over or resting on them. Worm tubes, as 
tJ. M. Clarke, op. cit., p. 205; J. B. Woodworth, ef al., “The Glacial Brick 
Clays of Rhode Island and Southeastern Massachusetts,” 17th Ann. Rept., U.S. 
Geol. Survey (1896), Part 1, p. 992; T. M’K. Hughes, “On Some Tracks of Ter- 
restrial and Fresh Water Animals,” Quar. Jour. Geol. Soc., London, Vol. XL, No. 157 
(1884), p. 184; J. E. Talmage, ‘‘Notes Concerning Certain Linear Marks in a Sedi- 
mentary Rock’’ (Abstract), Quar. Jour. Geol. Soc., London, Vol. LIL (1896), p. 461; 
Univ. Uiah Quarterly (December, 1895). 
2J. A. Udden, “Fossil Ice Crystals,” Univ. of Texas Bull. (1821), (1918); Scz. 
Amer., Vol. LXXII (1895), p. 102; ‘“‘A Sketch of the Geology of the Chisos Country, 
Brewster County, Texas,” Univ. of Texas, Bull. 93 (Science Series No. 11) (1907), 
p. 32; D.D. Christner and O. C. Wheeler, ‘“‘The Geology of Terrell County, Texas,” 
Univ. of Texas Bull. (1918), p. 15. 
