graptolite

noun

Any of a group of extinct aquatic colonial invertebrates, of the class Graptolithina, from the Cambrian and Carboniferous periods.

Graptolites are extinct marine animals that lived during the Paleozoic era.

意味（1）

Any of a group of extinct aquatic colonial invertebrates, of the class Graptolithina, from the Cambrian and Carboniferous periods.

The samples were black shale, and on the shales were some ancient fossils called graptolites.