Graptolite

GRAPTOLITE substantive (Gr. graphein, to write; lithos, rock). Genus of acaleph fossils, which includes at least 20 species found only in Silurian rocks, these fossils are long and thin, and they look like seaweed and sometimes like the barbed part of a pen, hence the name.
 
Extract from the Trousset encyclopedia, 1886 – 1891.