Note:  Do not rely on this information. It is very old.


Trinucleidae, a family of Trilobites (q.v.), in which the head sheild is greatly developed, and the two hinder angles of it are prolonged back as spines. The type-genus Trinucleus is most abundant in the Bala beds of North Wales, while the family is entirely restricted to the Silurian and Ordovician systems.