116 GEOLOGICAL REPORT—THIRTY-FIFTH PARALLEL. 
The specimen is a flat mass, about three inches square and one thick. It has a lamellar or 
stratified structure, and is traversed by cracks parallel with the sides, and which are caused 
apparently by the shrinking of the mass. The form is not quite square or rectangular, but is 
distinctly rhombic, and the cracks of the mass divide it up into smaller fragments, with the 
same angles. The streak or powder is dark-brown, and it makes a brown streak upon paper. 
On the surfaces of fracture, parallel with the broad surfaces of the specimen, there are distinct 
impressions of vegetation, but it is not possible to decide upon their character. On careful in- 
spection of the edges of the specimen, several thin layers, of what at first appear to be grains of 
sand, are seen. "These grains are the ends of small prismatic bodies, which are compact and 
of a drab color. They are striated longitudinally, and break, or cleave, readily in a direction 
perpendicular to the longer axis of the prism. These bodies are very probably the spines of 
fishes or echinoderms, but they are so imperfect and minute that their true nature cannot be 
satisfactorily determined. 
When this coal is heated it gives off a strong odor of bitumen, and burns with a white flame, 
and but little or no smoke, until the flame ceases, when the smoke is white like that from wood, 
When it is strongly ignited for a long time in the outer flame of the blow-pipe, it leaves a white 
skeleton residue, nearly as large as the original fragment. The edges of this on being strongly 
heated fuse to a white glass. à 
No. 99. Coal creek, Camp No. 12.—This is a fine specimen of Siggillaria, about nine inches 
long and four in diameter. The markings of the root are very distinctly preserved on one side, 
while the opposite is rough and not characteristic. 
No. 100. Camp No. 47, Arroyo Truxillo.—This, according to the label, is fossil wood of the 
Upper Trias. It is asilicified fragment of the trunk of a Lepidodendron—a well known plant of 
the Carboniferous period. The markings upon the surface are distinct and characteristic. 
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