Webster's 1913 Dictionary
GRAPTOLITE
Grap "to *lite, n. Etym: [NL, Graptolithus, from Gr. (Paleon.)
Defn: One of numerous species of slender and delicate fossils, of the genus Graptolites and allied genera, found in the Silurian rocks. They belong to an extinct group (Graptolithina ) supposed to be hydroids.
New American Oxford Dictionary
graptolite
grap to lite |ˈgraptəˌlīt ˈɡræptəlaɪt | ▶noun an extinct marine invertebrate animal of the Paleozoic era, forming mainly planktonic colonies and believed to be related to the pterobranchs. [Class Graptolithina, phylum Hemichordata. ] ORIGIN mid 19th cent.: from Greek graptos ‘marked with letters ’ + -lite: so named because of the impressions left on hard shales, resembling markings with a slate pencil.
Oxford Dictionary
graptolite
graptolite |ˈgraptəlʌɪt | ▶noun a fossil marine invertebrate animal of the Palaeozoic era, forming mainly planktonic colonies and believed to be related to the pterobranchs. ●Class Graptolithina, phylum Hemichordata. ORIGIN mid 19th cent.: from Greek graptos ‘marked with letters ’ + -lite: so named because of the impressions left on hard shales, resembling markings with a slate pencil.
The Wordsmith Dictionary