Twenty-five trilobite species belonging to twenty-three genera are rec
orded from the Caradoc Knockerk Formation of the Grangegeeth area, eas
tern Ireland. Arthrorhachis knockerkensis and Birmanites salteri are n
ew, while Barrandia sp, and Flexicalymene sp. possibly represent new s
pecies. The faunas occur predominantly in the lower parts of the Knock
erk House Sandstones Member and younger Brickwork's Quarry Shales Memb
er. The older fauna is of early Caradoc age and shows affinities with
species from the Balclatchie and Lower Ardwell groups at Girvan. The y
ounger trilobite fauna and associated graptolites are indicative of th
e Climacograptus peltifer Biozone (possibly Harnagian). The Laurentian
/Scoto-Appalachian affinities of the Grangegeeth Caradoc faunas indica
te that the Grangegeeth terrane was closest to Laurentia during the ea
rly Caradoc and that the final Iapetus Suture line must lie to the sou
th of the Grangegeeth terrane.