200 
Transactions Texas Academy of Science. 
Merrill, George P. 
Dolomite. Lower iSilurian; nearly white; coarsely crystalline. Near 
San 'Saba. 
1 Silurian; pink; fine and compact. Near San Saba. 
Ferruginous Dolomite. Silurian; fine and compact; pinkish, near San 
Saba. 
Limestone. Light-colored; fine; porous. Near Austin (two specimens). 
1 , Cretaceous; light-colored; fine; porous. Near Austin. 
Light-colored; fine; porous. Round Rock. 
Drab; compact. Near Burnet. 
Magnesian Limestone. Cretaceous; light-colored; fine; porous. Near 
Austin. 
Cretaceous; light-colored; fossiliferous. Near 
Austin. 
Biotite dranite. Fine; pink. Fight miles from Burnet. 
‘ Coarse; red. Eight miles from Burnet. 
Diorite. Medium; light greenish gray. Near El Paso. 
Sandstone. Lower Silurian; coarse; brown. Near Burnet. 
Lower Silurian; coarse; dull red. Near Burnet. 
' Carboniferous; fine; very light gray. Near Mormon Mills, 
Burnet county. 
306. Merrill, J. A. 
Possil Sponges of the Flint Nodules in the Lower Cretaceous of 
Texas. 
Bull, of the Museum of Comp. Zoology, Yoh XXYIII, No. 1, 
(Geol. Series, Yol. Ill,), p. 26, pi. 1. Cambridge, 1895. 
Contents: (Introduction.) A Statement of the Questions involved. 
Organisms found in the Flint. Condition of Preservation of the Sponge 
ISpicules. Comparison with English Chert. Classification of the Spicules. 
Monactinellidae, Zittel. Tetractinellidae, Marshall. Lithistidae, Oscar 
Schmidt. Hexactinellidae, Oscar Schmidt. Formation of the Nodules. 
Summary. 
“'So far as I have been able to ascertain, the minute structure of the 
Cretaceous flints of America has never been studied except in a general 
way, and nothing whatever has been published on the microscopic organ- 
isms composing them. The field is therefore a large as well as a fascinat- 
ing one, and this effort is intended only as a beginning of what is hoped 
will i>rove a fruitful line of inquiry. The flint nodules from which the 
.specimens were taken for study were collected in a quarry near Austin, 
Texas, land brought to Cambridge by Mr. Edward E. Cauthorne. They 
vary greatly in shape and size; and, owing, perhaps, to s, mall ' areas of 
calcite 'scattered through the mass, they vary somewhat in hardness. The 
hardnesis is often greater than that of glass, and the flint will generally 
scratch glass. In shape they are S'pherical, cylindrical, or flat; and in 
size 'they vary from two inches to a foot ot more in diameter. The color 
is dense ibla.ek. with white or gray spots mixed irregularly through it, 
varying in size from microscopic to that of a pin-head.” P. 1 . 
