graptolitic การใช้

• The Ordovician rocks are graptolitic black shales and grits of Llandeilo and Caradoc age.
• South-east of this line graptolitic Silurian shales of Llandovery age prevail; they are found around Dalry, Creetown, New Galloway, Castle Douglas and Kirkcudbright.
• The limits of Murchison's Caradoc series have since been somewhat modified, and through the labours of Charles Lapworth the several members of the series have been precisely defined by means of graptolitic zones.